WBBSE Class 10 Physical Science Solutions Chapter 8.4 Inorganic Chemistry in the Laboratory and in Industry

Detailed explanations in West Bengal Board Class 10 Physical Science Book Solutions Chapter 8.4 Inorganic Chemistry in the Laboratory and in Industry offer valuable context and analysis.

WBBSE Class 10 Physical Science Chapter 8.4 Question Answer – Inorganic Chemistry in the Laboratory and in Industry

A. Ammonia

Very Short Answer Type Questions

Question 1.
Name the chemicals required for the preparation of ammonia in laboratory
Answer:
Chemicals required :

• Ammonium chloride (NH₄Cl)
• Quick lime (CaO) or dry slaked lime [Ca(OH)₂]

Question 2.
What is the characteristic smell of ammonia ?
Answer:
Characteristic smell of ammonia Pungent

Question 3.
What is the nature of aqueous solution of ammonia ?
Answer:
Nature of aqueous solution of ammonia : alkaline

Question 4.
State one method for identification of ammonia.
Answer:
Ammonia has a typical pungent smell.

Question 5.
Which particular substance is used to dry ammonia gas ?
Answer:
Ammonia is dried with calcium oxide (CaO).

Question 6.
What colour is obtained when ammonia burns in presence of oxygen?
Answer:
Ammonia burns in presence of oxygen with a greenish yellow flame forming nitrogen and water.
4NH₃ + 3O₂ = 2N₂ + 6H₂O

Question 7.
What is Nessler’s reagent ?
Answer:
Nessler’s reagent Nessler’s reagent is an alkaline solution (KOH) of po­tassium mercuric iodide [K₂Hgl₄]

Question 8.
What happens when red litmus paper is placed in aqueous solution of ammonia ?
Answer:
The aqueous solution of ammonia is basic in nature so it turns red litmus to blue.

Question 9.
State one use of ammonium sulphate.
Answer:
Use of ammonium sulphate : as fertilizer.

Question 10.
What is the amount of ammonia present in liquor ammonia ?
Answer:
35% (by weight)

Question 11.
Is ammonia heavier or lighter than air ?
Answer:
Ammonia is lighter than air.
[Vapour density of air = 144 ; vapour density of ammonia = 8-5 ]

Question 12.
State one use of liquid ammonia.
Answer:
Use of liquid ammonia : as a refrigerant in ice making.

Question 13.
Give an example of formation of solid by the combination of two gases.
Answer:
Ammonia gas reacts with hydrogen chloride gas forming solid ammonium chloride.
NH₃(gas) + HCl (gas) = NH₄Cl (solid)

Question 14.
How is ammonia collected in laboratory ?
Answer:
Collection of ammonia Ammonia is lighter than air, it may be collected by the downward displacement of air.

Question 15.
What colour is obtained when ammonia reacts with Nessler’s reagent?
Answer:
Ammonia produces brown colouration in Nessler’s reagent.

Question 16.
Which compound of nitrogen has fractional oxidation number ?
Answer:
Hydrazoic acid (HN₃)
Nitrogen has \(\left(-\frac{1}{3}\right)\) oxidation number in hydrazoic acid.

Question 17.
Which hydride of nitrogen has no oxidising property ?
Answer:
Ammonia has no oxidising property.

Question 18.
Which gas is obtained when a mixture of ammonium sulphate and sodium hydroxide is heated ?
Answer:
Ammonia (NH₃) gas.

Question 19.
How ammonium sulphate is obtained without using sulphuric acid ?
Answer:
CaSO₄ + 2NH₃ + CO₂ + H₂O = CaCO₃ + (NH₄)₂SO₄

Question 20.
Two gaseous compounds of nitrogen react with each other to form nitrogen. What are the two gaseous compounds of nitrogen ?
Answer:

Short answer type questions

Question 1.
Why is conc. H₂SO₄ not used for drying ammonia gas ?
Answer:
Ammonia is a basic compound. So it forms salt with cone. H₂SO₄.
For this reason cone. H₂SO₄ is not used for drying ammonia gas.
2NH₃ + H₂SO₄ = (NH₄)₂SO₄

Question 2.
Why is anhydrous CaCl₂ not used for drying ammonia gas ?
Answer
Ammonia forms an additive compound with anhydrous CaCl₂.
CaCl₂ + 8NH₃ = CaCl₂, 8NH₃ (additive compound)

Question 3.
Why is P₂O_s not used for drying ammonia gas ?
Answer:
Ammonia is a basic compound. P₂O_s is an acidic oxide. So it forms salt with P₂O₅ SO P₂O₅ is not used for drying ammonia gas.
6NH₃ + P₂O_s + 3H₂O = 2(NH₄)₃PO₄

Question 4.
Why CaO is used for drying agent of ammonia ?
Answer:
CaO is used for drying agent of ammonia : Ammonia is a basic com­pound. It is dried of using a basic drying agent i.e. Quick lime (CaO) which has no action on ammonia.

Question 5.
What is liquor ammonia ?
Answer:
Liquor ammonia A saturated (35% by weight) aqueous solution of am­monia (sp. gr. = 088) is called liquor ammonia.

Question 6.
Prove that ammonia has reducing property.
Answer:
Reducing property of ammonia : When ammonia is passed over strongly heated black cupric oxide which is reduced to red metallic copper and am­monia is oxidised to nitrogen.

Question 7.
State about solubility of ammonia in water.
Answer
Solubility of ammonia is water : Ammonia is highly soluble in water. One volume of water can dissolve about 1299 volumes ammonia at N.T.P A concentrated aqueous solution of ammonia is called ammonia.

Question 8.
What are the differences between liquid ammonia and liquor ammonia ?
Answer
Difference between liquid ammonia and liquor ammonia :
There is a sharp difference between liquid ammonia and liquor ammonia. The first one is the liquified ammonia gas which has formula NH₃, while the second one is the concentrated solution of ammonia which has formula NH₄OH.

Question 9.
How will you prove that ammonia contains nitrogen ?
Answer
Ammonia contains nitrogen : Ammonia gas when passed over heated cupric oxide produces colourless gas having no smell.
3CuO + 2NH₃ = 3Cu + 3H₂O + N₂
When the colourless gas is passed over heated magnesium, magnesium nitride (Mg₃N₂), the white powder produces.
3Mg + N₂ = Mg₃N₂
When the white powder is boiled with water it will produce pungent smell gas NH₃
Mg₃N₂+ 6H₂O = 3Mg(OH)₂ + 2NH₃↑
This reaction proves that the colourless gas is nitrogen. This reaction also proves that one of the constituents of ammonia is nitrogen.

Question 10.
What precautions should be taken to combat the effect of ammonia leaked from industries and ammonia tanks ?
Answer
Precautions for ammonia If accidentally, ammonia gas leaks from indus­tries and ammonia tanks, heavy shower of water should be applied in the atmosphere that is filled with the leaked gas. If at any time, tanks filled with ammonia gas are required to be shifted somewhere, the carrier of tanks must also carry plenty of water that may be used to spray in the air filled with accidental leakage of ammonia gas.

Question 11.
How does ammonia react with sodium ?
Answer
Reaction of ammonia with sodium Heated sodium metal at 400°C reacts with ammonia producing sodamide and hydrogen gas.
2NH₃ + 2Na = 2NaNH₂ + H₂↑
This reaction proves that ammonia contains hydrogen.

Question 12.
How does ammonia react with chlorine ?
Answer
Reaction of ammonia with chlorine : Ammonia reacts with chlorine in two ways.
(i) When ammonia is excess : Excess ammonia is oxidised by chlorine forming nitrogen and is reduced to hydrochloric acid. Hydrochloric acid thus formed combines with ammonia producing ammonium chloride.

(ii) When chlorine is excess : When excess chlorine reacts ammonia forming nascent nitrogen which again combines with chlorine producing nitrogen trichloride, an oily yellow explosive compound.
NH₃ + 3Cl₂ = 3HCl + NCl₃

Question 13.
Show with an equation what happens when ammonia is burnt in oxygen.
Answer:
Ammonia is burnt in oxygen Ammonia is neither combustible nor a supporter of combustion. But ammonia burns in presence of oxygen with a greenish yellow flame forming nitrogen and water.
4NH₃ + 3O₂ = 2N₂↑ + 6H₂O

Question 14.
How does aqueous ammonia react with aluminium chloride and ferric chloride solutions ?
Answer:
(i) Reaction of aqueous ammonia with aluminium chloride solution: Aqueous solution of ammonia (NH₄OH) reacts with aluminium chloride forming white gelatinus precipitate of aluminium hydroxide.
AlCl₃ + 3NH₄OH = Al(OH)₃↓(white) + 3NH₄Cl

(ii) Reaction of aqueous ammonia with ferric chloride solution :
Aqueous solution of ammonia (NH₄OH) reacts with ferric chloride solution forming brown precipitate of ferric hydroxide.
FeCl₃ + 3NH₄OH = Fe(OH)₃↓(brown) + 3NH₄Cl

Question 15.
State with reasons two precautions taken during preparation of ammonia in laboratory.
Answer:
Precautions taken during preparation of ammonia in laboratory :

• The components ammonium chloride (NH₄Cl) and calcium hydroxide [Ca(OH)₂] should be dry to avoid evolution of ammonia while mixing the two.
• The mixture of the components should fill about half the flask to leave enough space for easy passage of the evolved gas.

Question 16.
State some uses of ammonia.
Answer:
Uses of ammonia :

• It is used for the industrial preparation of nitric acid and sodium carbonate.
• Large quantities of ammonia are used in the manufacture of fertilizers, such as urea, ammonium phosphate etc.
• Ammonia is used as solvent.
• Liquid ammonia is used as a refrigerant in ice making.
• Ammonia is used as laboratory reagent.
• It is also used in pharmaceutical industries and also in the preparation of smelling salt.

Question 17.
Give an example of formation of a solid by combination of two gases.
Answer:
Formation of a solid by combination of two gases : Ammonia gas reacts with hydrogen chloride gas forming a solid ammonium chloride. This is an example of formation of a solid by the combination of two gases.
NH₃ (gas) + HCl (gas) = NH₄Cl (solid)

Question 18.
State how does ammonia react with HCl, H₂SO₄, HNO, acids.
Answer:
Reaction of ammonia with acids : Ammonia is a base, it readily reacts with an acid to form salt.
NH₃ + HCl = NH₄Cl
2NH₃ + H₂SO₄ = (NH₄)₂SO₄
NH₃ + HNO₃ = NH₄NO₃
Aqueous solution of ammonia reacts with acids to form salt and water.
NH₄OH + HCl = NH₄Cl(salt) + H₂O₃
2NH₄OH + H₂SO₄ = (NH₄)₂SO₄(salt) + 2H₂O
NH₄OH + HNO₃ = NH₄NO₃(salt) + H₂O

Question 19.
How is urea obtained from ammonia?
Ans. Preparation of urea from ammonia: Ammonia reacts with carbon dioxide at 200°C and 150 atm pressure to form urea.
CO₂ + 2NH₃ = CO(NH₂)₂ (urea) + H₂O

Question 20.
How does aqueous ammonia react with copper sulphate solution?
Answer:
Reaction of aqueous ammonia with copper sulphate solution When aqueous ammonia i.e. ammonium hydroxide is slowly added to a copper sul­phate solution, a pale blue precipitate of basic copper sulphate is first formed. On adding excess of ammonium hydroxide, the precipitate dissolves forming a deep solution of the complex compound called copper tetramine sulphate.
2CuSO₄+ 2NH₄OH = CuSO₄. Cu(OH)₂ + (NH₄)₂SO₄
CuSO₄ .Cu(OH)₂ + 6NH₄OH + (NH₄)₂SO₄ = 2[Cu(NH₃)SO₄+ 8H₂O

Broad Answer Type Questions

Question 1.
How ammonia is prepared in laboratory ?
Answer:
Laboratory preparation of Ammonia :
(a) Chemicals required : Ammonium chloride (NH₄Cl) and quick lime (CaO) or dry slaked lime [Ca(OH)₂

(b) Condition Normally ammonia gas is obtained in the laboratory by heating a mixture of ammonium chloride with slaked lime. Instead of using slaked lime quick lime may also be used. NH₄>Cl, Ca(OH)₂ or CaO should be in powdered form and dry. The round bottomed flask should be half filled with the mixture of the two for easy escape of ammonia gas formed.

(c) Collection Ammonia is lighter than air, it may be collected by the downward displacement of air. Ammonia is not collected through the downward displacement of water because, it is highly soluble in water.

(d) Equations of the reaction :
2NH₄Cl + Ca(OH)₂ = 2NH₃↑+ CaCl₂ + 2H₂O
2NH₄Cl + CaO = 2NH₃↑ + CaCl₂ + H₂O

(e) Precautions : The ingradients, the test-tube, the delivery pipes and the gas-jar should be absolutely dry. All the connections in the apparatus should be leak-proof.

(f) Drying of ammonia : As ammonia is a basic substance, it cannot be dried by acidic drying agents like cone. H₂SO₄ or P₂O_s. The gas is absorbed by fused CaCl₂ with the formation of an addition compound CaCl₂.8NH₃. So, fused CaCl₂ cannot be used to dry ammonia. It is best dried with the basic drying agent, quick lime (CaO).

Question 2.
Prove by experiment that ammonia is dissolved in water and produces alkaline solution.
Answer:
Fountain experiment :
Arrangement of the experiment : A flask is filled with dry ammonia gas and its mouth is corked. The flask is kept in inverted position and is damped to a stand. Through a hole in the cork one end of a glass tube is introduced inside the flask. This end of the tube inside the flask is shaped into a jet. The other end of the tube dips in some red litmus solution taken in a beaker.

Operation : Now ice or ether is poured upon the flask.

Observation : A blue fountain produces inside the flask.

Explination Due to evaporation of ether the flask is cooled. Ammonia gas inside the flask contracts, as a result there is a partial vacuum inside the flask. At this stage if stop cock is opened the red litmus solution rushes inside the flask and ammonia is dissolved in it. Due to vaccum created inside there is a formation of fountain and the solution becomes blue.

Conclusion : This experiment proves that ammonia is highly soluble in water and the aqueous solution is alkaline.

Question 3.
How is ammonia identified ?
Answer:
Identification of ammonia :
(a) Ammonia is easily detected by its pungent smell.

(b) A glass rod dipped in into hydrochloric acid is then held into ammonia a white fumes is observed due to formation of ammonium chloride.
NH₃ + HCl = NH₄Cl (white fumes)

(c) Ammonia turns moist red litmus paper into blue.

(d) Ammonia produces brown colouration or precipitate in Nessler’s reagent.

(e) A strip of filter paper, soaked in mercurous nitrate solution, when exposed to ammonia gas, turns black.

B. Sulphuretted Hydrogen (H₂S)

Very Short answer type questions 

Question 1.
Which acid is used to prepare H₂S gas in laboratory ?
Answer:
Dilute sulphuric acid.

Question 2.
During preparation of H₂S gas in laboratory, how Is the gas collected?
Answer:
By upward displacement of air.

Question 3.
What happens when H₂S gas is passed through acidified yellow ferric chloride solution ?
Answer:
Yellow ferric chloride solution reduces to colourless ferrous chloride solution.

Question 4.
How is H₂S gas dried In laboratory preparation ?
Answer:
By passing the gas through phosphorus pentoxide (P₂O₅).

Question 5.
How does H₇S gas smell ?
Answer:
It has a smell of rotten egg.

Question 6.
How does H₂S gas react with blue litmus ?
Answer:
It turns blue litmus red.

Question 7.
What gas is used in detecting metallic radical in laboratory ?
Answer:
Sulphuretted hydrogen (H₂S)

Question 8.
Is H₂S gas heavier or lighter than air ?
Answer:
H₂S gas is heavier than air.

Question 9.
Is H₇S combustible or a supporter of combustion ?
Answer:
H₂S is a combustible gas.

Question 10.
Why is an old silver made substance turned to black ?
Answer:
Due to formation of silver sulphide (Ag₂S).

Question 11.
What is the common use of hydrogen sulphide in laboratory ?
Answer:
For the identification of basic radical (metal ion).

Question 12.
Name the chemicals required for preparation of H₂S in laboratory.
Answer:
Chemicals required for preparation of H₂S :

• Ferrous sulphide (FeS)
• Dilute sulphuric acid (H₂SO₄)

Question 13.
Is HCl acid suitable for preparation of H₂S ?
Answer:
No. As HCl is very volatile.

Question 14.
Mention one identifying test for H₂S.
Answer:
Lead acetate paper turns black when it is held in H₂S gas.

Question 15.
What is the density of H₂S at NTP ?
Answer:
Density of H₂S gas is 1-53 g/L at NTP

Question 16.
Give the name of a gas which is soluble in cold water but insoluble in hot water.
Answer:
Hydrogen sulphide (H₂S)

Question 17.
Which gas is used to identify basic radical ?
Answer:
Hydrogen sulphide (H₂S)

Question 18.
What happens when H₂S gas is passed through a blue coloured solution of CuSO₂ ?
Answer:
Black precipitate of CuS is formed.

Question 19.
Is H₂S acidic or basic gas ?
Answer:
H₂S is acidic gas.

Question 20.
How many types of salts are formed by H₂S ?
Answer:
Since H₂S is a bibasic acid, it gives two types of salt, one is acid salt and other is normal salt.

Question 21.
Give the name of a poisonous gas.
Answer:
Hydrogen sulphide (H₂S).

Short Answer Type Questions

Question 1.
Name the chemicals required for preparation of H₂S in laboratory. Write down the equation of reaction.
Answer:
Chemicals required for preparation of H₂S in laboratory :
Ferrous sulphide (FeS) and dilute sulphuric acid (H₂SO₄)
Equation : FeS + H₂SO₄ = FeSO₄ + H₂S↑

Question 2.
Is HCl acid suitable for preparation of H₂S ? Give reason.
Answer:
HCl acid is not suitable for preparation of H₂S.
Cause : HCl acid is not chosen due to volatile nature of HCl. During the preparation, HCl vapour that may be formed will accompany the evolved H₂S and will make it impure.

Question 3.
Is HNO₃ acid suitable for preparation of H₂S? Give reason.
Answer:
HNO₃ acid is not suitable for preparation of H₂S.
Nitric acid cannot be used in the preparation, because it is an oxidising agent and H₂S is a reducing agent. Nitric acid will oxidise H₂S to sulphur and will thus hamper the reaction.

Question 4.
Mention one identifying test for H₂S.
Answer:
Identification of H₂S: Hydrogen sulphide is passed through a solution of sodium hydroxide solution and then sodium nitroprusside solution is added to it. The solution turns violet.

Question 5.
How does H₂S react with cone. HNO_a?
Answer:
Reaction of H₂S with cone HNO₃ :
H₂S-reduces cone. HNO₃ to brown nitrogen dioxide (NO₂) and is itself oxidised to sulphur.
Equation : H₂S + 2HNO₃ = 2NO₂↑ + S↓+ 2H₂O

Question 6.
How does H₂S react with cone. H₂SQ₄ ?
Answer:
Reaction of H S with cone. H₂SO₄ : H₂S) reduces cone. H₂SO₄ to SO₂ and is itself oxidised to sulphur.
Equation : H₂S + H₂SO₄ = SO₂↑ + S↓ + 2H₂O

Question 7.
Write down the reaction of H₂S with NaOH.
Answer:
Reaction of H₂S with NaOH : H₂S reacting with NaOH produces acid salt in the first step and normal salt in the second step along with water in both the steps.

Question 8.
Which substance is used for drying H₂S and why ?
Answer:
Drying of H₂S gas : The most suitable drying agent for H₂S is the acidic oxide P₂O₅, that does not react with H₂S which is also of acidic nature.

Question 9.
What is the density of H₂S and state about its solubility in water at ordinary temperature and in hot water.
Answer:
Density of H₂S : Density of the gas is T53 g/L at NTR
Solubility of H₂S in water : It is moderately soluble in water at ordinary temperature but insoluble in hot water.

Question 10.
What happens when H₂S is burnt in small and excess supply of oxygen ?
Answer:
H₂S is burnt in small supply of oxygen : During burning of H₂S if the supply of oxygen is low, the gas burns with a blue flame and deposits sulphur. 2H₂S + O₂ = 2S↓ + 2H₂O
H₂S is burnt in excess supply of oxygen : In an excessive supply of oxygen the gas burns with a blue flame and produces sulphur dioxide and water.

Question 11.
Show that H₂S is a reducing agent.
Answer:
Reducing property of H₂S : Hydrogen sulphide is a very good reducing agent. H₂S reduces acidified yellow solution of ferric chloride to colourless ferrous chloride.

Question 12.
What happens when H₂S is passed through acidified solution of FeCl_a?
Answer:
Yellow ferric chloride solution is reduced by H₂S giving rise colourless ferrous chloride and H₂S itself on oxidation gives a precipitate of sulphur.
Equation : 2FeCl₃ + H₂S = 2FeCl₂ + 2HCl + S₄

Question 13.
What happens when H₂S is passed through acidified solution of CuSO₄?
Answer:
If H₂S is passed through acidified blue coloured solution of CuSO₄ then black precipitate of cupric sulphide (CuS) is formed.
Example:

Question 14.
What happens when H₂S is passed through acidified solution of Pb(NO₃)₂
Answer:
If H₂S is passed through acidified colourless solution of Pb(NO₃)₂ then black precipitate of lead sulphide (PbS) is formed.
Example:

Question 15.
What happens when H₂S comes in contact with a paper soaked in lead acetate ?
Answer:
A paper soaked in lead acetate [Pb(CH₃COO)₂] turns black with H₂S gas due to formation of black lead sulphide (PbS).
Equation:

Question 16.
Mention the uses of hydrogen sulphide.
Answer:
Uses of hydrogen sulphide :

• H₂S is used as a reagent in the separation of metal ions in group analysis.
• H₂S is sometimes used as a reducing agent.

Broad answer type questions

Question 1.
Describe laboratory method of preparation of H₂S with the points:
(i) chemicals required
(ii) condition
(iii) equation of reaction
(iv) drying agent
(v) collection
Answer:
(i) Chemicals required Ferrous sulphide (FeS) and dilute sulphuric acid (H₂SO₄)
(ii) Condition Hydrogen sulphide is prepared in the laboratory by the action of dil. H₂SO₄ on pieces of ferrous sulphide (FeS) at ordinary temperature.
(iii) Equation of reaction : FeS + H₂SO₄ = FeSO₄ + H₂S↑
(iv) Drying agent The gas is passed through P₂O₅ to dry it.
(v) Collection : Because the gas is heavier than air it is collected over the upward displacement of air.

Question 2.
What precautions should be taken during preparation and handling of H₂S ?
Answer:
Precautions taken during preparation of H₂S : Hydrogen sulphide is a poisonous gas and is harmful at concentrations above 0-1% by volume in air. So, due precautions should be taken not to inhale the gas not to allow its prolonged contact with skin during handling.

During preparation of the gas caution must be taken so that excessive gas does not spread in the atmosphere of laboratory. To do this, sulphuric acid should be added in the wolfe’s bottle in small quantities and in steps.

C. Nitrogen

Very short answer type questions

Question 1.
Name the chemicals used In laboratory method of preparation of nitrogen.
Answer:
Chemicals required : Ammonium chloride (NH₄Cl) and sodium nitrite (NaNO₂).

Question 2.
State what you know about solubility of nitrogen in water.
Answer:
Solubility of nitrogen in water is about 23-5 ml/L at NTR It is almost half that of oxygen.

Question 3.
What is the density of nitrogen?
Answer:
Density of nitrogen 125 g/L at NTR

Question 4.
How is nitrogen prepared in laboratory dried?
Answer:
Nitrogen has is dried by passing the gas through concentrated sulphuric acid (H₂SO₄).

Question 5.
What is the percentage of nitrogen in air by volume?
Answer:
Percentage of nitrogen in air by volume : 77 17%

Question 6.
What would happen if there were no nitrogen in the atmosphere?
Answer:
In absence of nitrogen burning in atmosphere would be vigorous and uncontrollable.

Question 7.
What is the use of liquid nitrogen?
Answer:
Liquid nitrogen (b.p.-195’8°C) is used to produce low temperature in scientific research.

Question 8.
Is nitrogen heavier or lighter than air?
Answer:
Nitrogen is slightly lighter than air.

Question 9.
Give a name of nitrogen containing inorganic fertilizer.
Answer:
Nitrogen containing inorganic fertilizer : Ammonium nitrate (NH₄NO₃).

Question 10.
Which gas is used in gas-thermometer?
Answer:
Nitrogen gas is used in gas-thermometer.

Question 11.
Which gas is used in electric bulb?
Answer:
Nitrogen gas is used in electric bulb.

Question 12.
What is nitrogen trihydride?
Answer:
Nitrogen trihydride is ammonia

Question 13.
Which gas is presentjarge amount in atmosphere?
Answer:
Nitrogen gas is present large amount in atmosphere.

Question 14.
What is nitrolim?
Answer:
Nitrolim : Mixture of calcium cyanamide and carbon is known as nitrolim.

Question 15.
Which gas is used to create inert atmosphere during^hemical reactions.
Answer:
Nitrogen gas is used to create inert atmosphere during chemical reactions.

Question 16.
What are the two essential gaseous components of the atmospheric air ?
Answer:
Two essential gaseous components are :
(i) Oxygen
(ii) Nitrogen

Question 17.
Which plants absorb nitrogen directly from air ?
Answer:
A few leguminous plants such as pea, bean, clover etc. can absorb nitrogen directly from air.

Question 18.
What are the ways of fixation of nitrogen?
Answer:
There are two ways of fixation of nitrogen:
By electric discharge
Bio-chemical reaction through bacteria.

Short Answer Type Questions

Question 1.
How does nitrogen react with oxygen?
Answer:
Reaction of nitrogen with oxygen : Nitrogen reacts with oxygen forming nitric oxide under the influence of electric arc at a temperature of 3000°C.
\(\mathrm{N}_2+\mathrm{O}_2 \rightleftharpoons 2 \mathrm{NO} \text { – heat (Endothermic reaction) }\)

Question 2.
Why Is the solution of ammonium chloride and sodium nitrite is heated to produce nitrogen instead of heating ammonium nitrite directly?
Answer:
Nitrogen gas is not prepared by heating ammonium nitrite (NH4NO2) directly, for in that case rapid explosive dissociation of ammonium nitrite takes place.

Question 3.
How does nitrogen react with magnesium ?
Answer:
Reaction with magnesium : When turnings of magnesium metal are strongly heated in nitrogen gas, the metal directly combines with nitrogen to form magnesium nitride
(Mg₃N₂).
3Mg + N₂ = Mg₃N₂

Question 4.
What happens if magnesium nitride is boiled with water ?
Answer:
Magnesium nitride is boiled with water to form magnesium hydroxide and ammonia.
Mg₃N₂ + 6H₂O = 3Mg(OH)₂ + 2NH₃ 

Question 5.
What is nitrolim? How it is formed? Mention its important use.
Answer:
Nitrolim: When small lumps of white calcium carbide (CaC₂) are heated in nitrogen gas at about 1100°C, calcium cyanamide (CaNCN) is formed, along with the separation of carbon particles (black). The blackish brown mixture of the products (CaNCN + C) is commercially known as nitrolim. Use of nitrolim : It is largely used as a fertilizer.

Question 6.
State the uses of nitrogen.
Answer:
Uses of nitrogen :

• It is used in the industrial preparation of ammonia and nitric acid.
• It is used for the production of fertilizer, such as ammonium sulphate, am­monium nitrate.
• Liquid nitrogen (b.p. -195’8°C) is used as condenser.
• In many chemical reactions, nitrogen is used as inert medium.
• It is used in the preparation of electric bulb and gas thermometer.

Question 7.
Why gaseous nitrogen is chemically quite inactive at ordinary temperatures, but it is active at higher temperatures ?
Answer:
Chemical nature of gaseous nitrogen : The unreactivity of nitrogen at ordinary temperatures, is due to the structure of nitrogen molecule (N₂), in which two nitrogen atoms are bonded together by three covalent bonds (N ≡ N). The force of attraction of two nitrogen atoms so bonded is very high. So large amount of energy (generally heat energy) is required to break up this bond to set free the two nitrogen atoms so that they can enter into chemical combination.

Question 8.
State the physical properties of nitrogen.
Answer:
Physical properties of nitrogen :

• It is colourless gas without smell or taste,
• Density of the gas is 1.25 g/L at NTR
• It is slightly soluble in water.
  Solubility of nitrogen in water is about 23-5 ml/L at NTR

Broad Answer Type Questions 

Question 1.
Describe the laboratory method of preparation of nitrogen. State the following matters :
(a) chemicals required
(b) condition
(c) drying
(d) chemical equation
(e) collection of gas.
Answer:
Laboratory method of preparation of nitrogen :
(a) Chemicals required :

• Sodium nitrite (NaNO₂)
• Ammonium chloride (NH₄Cl)

(b) Condition : The chemicals ammonium chloride and sodium nitrite must not be in solid state but as solution. The mixture is heated gently to evolve nitrogen gas.

(c) drying : The nitrogen gas is dried by passing through a U-tube containing cone., sulphuric acid.

Chemical equation:

(e) Collection of gas : Though nitrogen gas is slightly soluble in water, it is collected by the downward displacement of water.

Question 2.
State briefly the significance of the presence of nitrogen in air.
Answer:
Significance of the presence of nitrogen in air : Nitrogen in air dilutes oxygen present therein. Oxygen is a very active oxidant. The mixture of nitrogen with oxygen in air moderates the intense activity of pure oxygen in the processes of respiration, combustion etc, which would have otherwise occurred very rapidly.

The intake of only oxygen during respiration would have caused increased rate of respiration, causing excessive burning of body tissues. This would have caused high and unchecked rise in the temperature of body, which results death. Without nitrogen in air, the combustion of earthly materials would have been explosively vigorous.

The huge amount (about 78% by volume) of nitrogen in air can be ab­sorbed by certain symbiotic bacteria, such as Rhizobium leguminouserum, R. japonicum etc. Nitrogen is converted to nitrogenous salts in nature by many chemical and biochemical process. Proteins, the complex nitrogenous compounds, which are absolutely essential for living beings are also indirectly formed from the nitrogen of air.

Question 3.
State the two possible ways of reaction of nitrogen with hydrogen, also write down the connected equations of reaction.
Answer:
First type Nitrogen combines with hydrogen under the influence of electric spark producing ammonia gas.

Second type : Nitrogen also combines with hydrogen at 550°C under 200 atmospheric pressure in presence of iron catalyst to form nitrogen gas.

Question 4.
State two important ways of fixation of nitrogen.
Answer:
Two ways of fixation of nitrogen :
By electric discharge : During electric discharge in the atmosphere nitrogen and oxygen present in air combine to produce nitric oxide. The produced nitric oxide is then oxidised by atmospheric oxygen to form nitrogen dioxide. Later this oxide upon missing with water vapour or rain water product nitric acid which falls upon our earth.

Nitric acid is then reacted with the bases present in the soil forming nitrate salts.

iii. Fixation of nitrogen due to bacteria Some micro organism and blue green algae convert nitrogen present in air to ammoiate salt by bio-chemical process. When the animal and plant bodies undergo decay most of the nitrogen (proteins) is liberated as ammonia which is oxidised in the soil by the combined action of nitrosifying and nitrifying becteria into nitrate to be again assimilated by plants. A portion of the fixed nitrogen is set free by the action of denitrifying bacteria of the soil.

(d) Hydrogen Chloride (Hydrochloric acid),
Nitric acid and Sulphuric acid

Very Short Answer Type Questions )

Question 1.
Why is concentrated sulphuric acid used to prepare HCl in laboratory ?
Answer:
Concentrated sulphuric acid is used to prepare HCl in laboratory because concentrated sulphuric acid is less volatile.

Question 2.
What is muriatic acid ?
Answer:
Muriatic acid is the commercial name of hydrochloric acid (HCl).

Question 3.
Why is not nitric acid used to prepare HCl ?
Answer:
Nitric acid is not used to prepare HCl as nitric acid is highly volatile and a strong oxidant.

Question 4.
State about solubility of HCl gas in water ?
Answer:
HCl gas is highly soluble in water.

Question 5.
Why is not hydrochloric acid used to prepare nitric acid ?
Answer:
Hydrochloric acid is not used to prepare nitric acid as hydrochloric acid is more volatile than nitric acid.

Question 6.
What is fuming nitric acid ?
Answer:
Fuming nitric acid is a product produced by dissolving excess nitrogen di­oxide in nitric acid.

Question 7.
What is acid rain ?
Answer:
Dissolved NO₂and SO₂ of atmosphere produce acids which come down along with rain. This is called acid rain.

Question 8.
What is oleum ?
Answer:
Oleum is sulphuric acid in which excess sulphur trioxide is dissolved.

Question 9.
What is stone cancer ?
Answer:
Corrosion of marble or stone due to acid rain is called stone cancer.

Question 10.
What is the commercial name of nitric acid ?
Answer:
The commercial name of nitric acid is aqua fortis.

Question 11.
How does copper react with sulphuric acid ?
Answer:
Copper reacts with hot and concentrated sulphuric acid.

Question 12.
Why does sugar of white colour turns to a black mass in contact with concentrated sulphuric acid ?
Answer:
Concentrated sulphuric acid absorbs the water molecules present in sugar molecules leaving behind black carbon.

Question 13.
What is passive iron ?
Answer:
Chemically inactive iron is called passive iron.

Question 14.
What is the commercial name of sulphuric acid ?
Answer:
The commercial name of sulphuric acid is oil of vitriol.

Question 15.
Which acid produces hydrogen reacting with metals Mg and Mn only?
Answer:
Dilute and cold nitric acid (HNO₃) produces hydrogen reacting with Mg and Mn.

Question 16.
Name an acid which has great affinity to water.
Answer:
Concentrated sulphuric acid (H₂SO₄) has great affinity to water.

Question 17.
Which acid is identified by ring test ?
Answer:
Nitric acid is identified by ring test.

Question 18.
Which acid turns blue copper sulphate to white anhydrous salt ?
Answer:
Concentrated sulphuric acid (H₂SO₄) turns blue copper sulphate to white anhydrous salt.

Question 19.
Among HCl, H₂SO₄ and HNO₃ acid which acid has the lowest boiling point ?
Answer:
HCl acid has the lowest boiling point.

Question 20.
What is aqua regia ?
Answer:
Aqua regia is a mixture of 3 volumes concentrated hydrochloric acid and 1 volume concentrated nitric acid.

Question 21.
Which acid is detected by AgNO₃ solution ?
Answer:
Hydrochloric acid is detected by AgNO₃ solution.

Question 22.
What is royal water ?
Answer:
Aqua regia is also known as royal water.

Question 23.
What is fuming sulphuric acid ?
Answer:
Fuming sulphuric acid or oleum is obtained when sulphur trioxide is passed over 98% sulphuric acid.

Question 24.
How is hydrogen chloride gas collected in laboratory ?
Answer:
Hydrogen chloride gas is heavier than air so it is collected by upward dis­placement of air.

Question 25.
Name one air pollutant gas.
Answer:
Air polutant gas is nitrogen dioxide (NO₂)

Question 26.
Which gas pollutes air form Goldsmith’s workshop ?
Answer:
Nitrogen dioxide (NO₂)

Question 27.
Which mineral acid has no reducing property ?
Answer:
Nitric acid (HNO₃)

Question 28.
What is the commercial name of nitric acid ?
Answer:
The commercial name of nitric acid is aquafortis.

Question 29.
State one use of aqua regia.
Answer:
Noble metals like gold, platinum are soluble in aqua regia.

Question 30.
State one use of sulphuric acid.
Answer:
Sulphuric acid is used to prepare fertilizer like ammonium sulphate [NH₂SO₄]

Question 31.
State one use of nitric acid.
Answer:
Nitric acid is used for the manufacture of high explosive like nitroglycerine.

Question 32.
Name a reducing acid.
Answer:
Hydrochloric acid (HCl) is an example of reducing acid.

Question 33.
What is the catalyst used during preparation of nitric acid by the Ostwald process ?
Answer:
Platinum gauze catalyst is used during preparation of nitric acid by the Ostwald process.

Question 34.
Which catalyst is used during preparation of sulphuric acid by contact process ?
Answer:
Platinum asbestos or vanadium pentoxide catalyst is used during preparation of sulphuric acid by contact process.

Question 35.
Which acid is detected by BaCl, solution ?
Answer:
Sulphuric acid (H₂SO₄) is detected by BaCl solution.

Question 36.
What is the basicity of sulphuric acid ?
Answer:
The basicity of sulphuric acid is 2.

Question 37.
Which acid is used as a cleaning agent in bathroom ?
Answer:
Muriatic acid (HCl) is used as a cleaning agent in bathroom.

Question 38.
Among HCl, H₂SO₄ and HNO which acid has the highest point?
Answer:
Sulphuric acid has the highest boiling point [338°C] among HCl, H₂SO₄ and HNO₃

Question 39.
Which acid is called ‘king of chemicals’ ?
Answer:
Sulphuric acid (H₂SO₄) is called ‘king of chemicals’.

Question 40.
Which acid is gas at ordinary temperature ?
Answer:
Hydrochloric acid.

Question 41.
Dense white fumes are formed when a glass-rod, moistened with strong ammonia solution, is held in a gas. Identify the gas.
Answer:
The gas is ammonia.

Question 42.
What is laughing gas ?
Answer:
Nitrous oxide (N₂O) is called laughing gas.

Question 43.
Can dry hydrogen chloride gas turn blue litmus paperred ?
Answer:
No. Dry hydrogen chloride gas turns a moist blue litmus paper red.

Question 44.
What is the molecular weight of nitric acid ?
Answer:
The molecular weight of nitric acid is 63.

Question 45.
What is the specific gravity of sulphuric acid ?
Answer:
The specific gravity of sulphuric acid is 1.84.

Question 46.
Name one metal ion that can be identified by using H₂S.
Answer:
Cu²⁺

Question 47.
What is commercial name of pyrosulphuric acid?
Answer:
Oleum (H₂S₂O₇)

Question 48.
What is the catalyst used for preparation of HNO₃ by ‘ostwald process’
Answer:
Platinum wie gauze is used as the catalyst for the purpose.

Question 49.
What is liquor ammonia?
Answer:
Liquor ammonia is a saturated solution of ammonia in water.

Question 50.
What is Nessler’s reagent?
Answer:
Alkaline solution of potassium tetra iodo mercurate, K₂[Hgl₄] is known as Nessler’s neagent.

Question 51.
What is aqua fortis?
Answer:
Nitric acid (HNO₃) was known to the alchemists as aqua fortis.

Question 52.
Why do old oil paintings turn black on exposure to H₂S?
Answer:
The paints used in oil paintings contain lead that react with weak dibasic H₂S to form black lead sulphide (PbS).

Question 53.
Name a gas which can be prepared in kipp’s apparatus.
Answer:
H₂S can be readily and intermittently prepared in kipp’s apparatus.

Question 54.
What happens when calcium cyanamide is heated with super heated steam?
Answer:
When calcium cyanamide is heated with super heated steam (especially in an autoclave), it is hydrolysed to form ammonia.

Question 55.
What happens when ammonia is burnt in air?
Answer:
When ammonia is burnt in air, it burns with a greenish-yellow flame forming nitrogen and steam.

Question 56.
H₂SO₄ is industrially produced by which process?
Answer:
H₂SO₄ is industrially produced by contact process.

Question 57.
Why H₂S gas is collected by upward displacement of air?
Answer:
H₂S is soluble in cold water and is heavier than air. So it is not collected over water and is collected by upward displacement of air.

Short Answer Type Questions

Question 1.
Describe the preparation of hydrogen chloride in laboratory with mention of
(i) chemical equation
(ii) collection
Answer:
Preparation of hydrogen chloride in laboratory : Chemical equation:
(i) If the mixture of sodium chloride and concentrated sulphuric acid is heated at 150°C – 200°C then sodium bisulphate and hydrogen chloride gas are produced.

(ii) If it is heated at 500°C then sodium sulphate and hydrogen chloride gas are evolved.

Collection : Since dry hydrogen chloride gas is heavier than air it is col­lected by upward displacement of air.

Question 2.
Why the reaction is kept at lower temperature during the preparation of hydrogen chloride in laboratory from sodium chloride and cone, sulphuric acid ?
Answer:
Reason In the laboratory the reaction is kept at lower temperature because:

• at high temperature the flask used in the preparation may be cracked.
• Sodium sulphate at higher temperature forms a hard crust and sticks to the glass. Its removal is then difficult.

Question 3.
Why hydrogen chloride is not collected over displacement of water?
Answer:
Reason : Hydrogen chloride is highly soluble in water. It has been found that at 0°C, 450 ml of hydrogen chloride is dissolved in 1 ml of water. So, it is not collected over displacement of water.

Question 4.
What is the compound necessary for drying of hydrogen chloride gas?
Answer:
Drying of hydrogen chloride : To remove water vapour, hydrogen chloride gas is passed over cone. H₂SO₄.

Hydrogen chloride is acidic nature. Hence, it cannot be dried over quick lime (CaO), caustic soda (NaOH) or caustic potash (KOH).

Question 5.
How is hydrochloric acid prepared ?
Answer:
Preparation of hydrochloric acid : Hydrochloric acid is a solution of hydrogen chloride gas in water. Cone, hydrochloric acid, as used in the laboratory is not 100% pure hydrochloric acid. It is about 38% solution of hydrogen chloride gas in water.

Hydrogen chloride gas is passed into a beaker containing cold water till the water is saturated with the gas. The contents of the beaker is a concentrated solution of hydrochloric acid.

Question 6.
Hydrochloric acid is not prepared by dissolving hydrogen chloride gas in water directly—why ?
Answer:
Reason As hydrogen chloride gas is highly soluble in water and the rate of dissolving of HCl gas in water is much higher than the rate of formation of HCl gas as a result there is a vacuum in the flask. To fill up the vacu­um water in the beaker enters into the flask and creates explosion when it contacts with sulphuric acid present in the flask.

Question 7.
Nitric acid is not used in the preparation of hydrochloric acid—why?
Answer:
Explanation :
(a) Nitric acid is not used because during the preparation of hydrogen chloride gas, nitric acid oxidises the evolved hydrogen chloride gas into chlorine gas.
Reaction HNO₃ + _;3HCl = NOCl + 2[Cl] + 2H₂O

(b) Hydrochloric acid (b. p. 86°C) and hydrogen chloride are volatile in nature. So they will be collected jointly in a receiver where nitric acid may oxidise hydrogen chloride into chlorine. On the other hand H₂SO₄(b.p. 338°C) is non-volatile; so, this is not happened.

Question 8.
State two physical properties of HC:
Answer:
Physical properties of HCl:

• It is a colourless gas with a choking smell and strongly fuming in moist air, hydrogen chloride is 127 times as heavy as air ; it neither burns nor supports burning.
• It is highly soluble in water. At 0°C, 450 ml of hydrogen chloride gas is dissolved in 1 ml of water.

Question 9.
How is pure hydrogen chloride prepared ?
Answer:
Preparation of pure hydrogen chloride Pure hydrogen chloride is obtained by the action of water upon silicon tetrachloride. Equation : SiCl₄ + 4H₂O = Si(OH)₄ + 4HCl

Question 10.
State the reaction of HCl with Na.
Answer:
Hydrogen chloride neither burns in air nor supports combustion. However burning sodium continues to burn in the gas with a bright yellow flame producing hydrogen and anhydrous sodium chloride.
Equation : 2Na + 2HCl = 2NaCl + H₂↑

Question 11.
Show the acidic property of hydrochloric acid.
Answer:
The aqueous solution of hydrochloric acid is a strong acid :

dissolves base metals, liberating hydrogen and forming metallic chlorides,
e.g. Zn + 2HCl = ZnCl₂ + H₂↑
The order of activity of the metals for liberating hydrogen may be stated as:
Ca > Mg > Al > Zn > Fe > Sn.

Question 12.
How copper and silver react with hydrochloric acid ?
Answer:
Generally, copper, silver are not attacked by hydrochloric acid. In presence of air, copper and silver react with very slowly producing corresponding chlorides and water.
Equations :

• 2Cu + 4HCl + O₂ = 2CuCl2₂ + 2H₂O
• 4Ag + 4HCl + O₂ = 4AgCl + 2H₂O

Question 13.
How does ammonia react with hydrogen chloride
Answer:
Reaction of ammonia with hydrogen chloride : Ammonia in contact with hydrogen chloride gives dense white fumes of solid ammonium chlo­ride. This reaction is an example of the formation of a solid product by the interaction of two gases.
Equation : NH₃(g) + HCl(g) = NH₄Cl(s)

Question 14.
What is reaction between Na₂CO₃ and HCl ?
Answer:
Reaction of Na₂CO₃ with HCl :
HCl reacts with Na₂CO_s to literate carbon dioxide.
Na₂CO₃ + 2HCl = 2NaCl + CO₂↑ + H₂O

Question 15.
State the action of hydrochloric acid with oxidising agent like MnO₂ and KMnO₄.
Answer:
Reaction of hydrochloric acid with MnO₂and KMnO₄
Manganese dioxide (MnO₂ oxidises hot and concentrated hydrochloric acid to greenwish yellow chloride.Potassium permanganate oxidises the hydrochloric acid at the ordinary tem­perature.

Question 16.
Show the presence of chloride ion in hydrochloric acid.
Answer:
Presence of chloride ion in hydrochloric acid : When hydrochloric acid is added to a solution of silver nitrate, a white precipitate of the chloride of silver is obtained. Silver chloride is insoluble in nitric acid but soluble in ammonium hydroxide.
Equation : AgNO₃ + HCl = AgCl↓ + HNO₃ 

Question 17.
How is hydrochloric acid identified?
Answer:
Identification of hydrochloric acid : When silver nitrate solution is added to hydrochloric acid taken in a test tube, curdy white precipitate of silver chloride is formed. The precipitate is insoluble in nitric acid but dissolves in ammonium hydroxide forming a clear solution of complex salt argento ammonium chloride. Equations :

• AgNO₃ + HCl = AgCl↓ + HNO₃
• AgCl + 2NH₄OH = [Ag(NH₃)₂]Cl + 2H₂O

Question 18.
State the identification of hydrogen chloride gas.
Answer:
Identification of hydrogen chloride gas : Dense white fumes are formed when a glass-rod, moistened with strong ammonia solution, is held in the hydrogen chloride gas.
Equation : NH₃(g) + HCl (g) = NH₄Cl (s)

Question 19.
What are the uses of hydrochloric acid ?
Answer:
Uses of hydrochloric acid :

• It is used in dyeing and calico-printing,
• It is used as a cleaning agent in galvaning and tinplating,
• It is used to prepare aqua-regia,
• It is used in the manufacture of glucose, glue and many useful metal-chlorides.

Question 20.
Describe the preparation of nitric acid in laboratory with mention of
(i) chemical required
(ii) chemical reaction.
Answer:
Preparation of nitric acid in laboratory :
Chemical required :

• Chille salt petre (NaNO₃) or nitre (KNO₃)
• Cone. Sulphuric acid.

Reaction occurs in two steps :

(a) If the reaction is kept at 200°C-300°C then sodium bisulphate and nitric acid are produced.

(b) At 800°C, sodium sulphate and nitric acid are formed in the reaction between sodium nitrate and concentrated sulphuric acid.
2NaNO₂+ H₂SO₄ = Na₂SO₄ + 2HNO₄

Question 21.
Why nitric acid is prepared at lower temperature (200°C) in laboratory?
Answer:
Nitric acid is prepared at lower temperature (200°C) in laboratory because :

• At high temperature nitric acid decomposes.
  4HNO₃ = 4NO₂ + O₂ + 2H₂O
• Nitric acid vapour attacks glass surface of the retort.
• Sodium sulphate (Na₂SO₄) formed at the higher temperature sticks to glass and is difficult to remove from the glass retort.

Question 22.
Why is cone, sulphuric acid used instead of cone, hydrochloric acid in the preparation of nitric acid in laboratory ?
Answer:
Choice of acid : In the preparation of an acid, the reacting acid must be less volatile than the acid to be prepared.Hence, cone. H₂SO₄(b.p. 338°C) is chosen because it is less volatile than nitric acid (b.p. 86°C). Hydrochloric acid is more volatile than nitric acid, so hydrochloric acid is not used. Beside this hydrochloric acid reacts with produced nitric acid to form nitrosyl chloride, chlorine and water.
3HCl + HNO₃ = NOCl + Cl₂ + 2H₂O

Question 23.
What is fuming nitric acid ?
Answer:
Fuming nitric acid : It is brown coloured liquid. It is actually cone. HNO₃ containing dissolved nitrogen dioxide (NO₂) gas. The dissolved nitrogen di­oxide spontaneously comes out of the liquid as brown fumes. That is why, it is called fuming nitric acid.

Preparation of fuming nitric acid : It is prepared by distilling cone, nitric acid with starch or arsenious oxide (As₂O₃).

Property and use of fuming nitric acid : Fuming nitric acid is a stronger oxidising agent than ordinary cone, nitric acid. It is used for many oxidation purposes where ordinary nitric acid does not give satisfactory results.

Question 24.
State the preparation of nitric acid by Ostwald process.
Answer:
Preparation of nitric acid by Ostwald process (1914) :

• In this process ammonia is oxidised in presence of heated (750°C-900°C) platinum gauze catalyst by oxygen in air to produce nitric oxide.
  4NH₃ + 5O₂ = 4NO↑ + 6H₂O + 218,660 cal
• The gases containing nitric oxide (NO) and steam (H₂ are cooled and then mixed with air to oxidise nitric oxide to nitrogen dioxide.
  2NO + O₂ = 2NO₂
• Nitrogen dioxide, is then absorbed in water to yield a 50% solution of nitric acid and nitric oxide.
  3NO₂ + H₂O = 2HNO₃ + NO↑

Question 25.
What are the physical properties of nitric acid ?
Answer:
Physical properties of nitric acid :

• Pure nitric acid is a colourless, fuming liquid of specific gravity 152 at 15°C,
• It boils at 86°C and freezes at -42°C into a transparent crystalline substance.
• It is highly soluble in water.

Question 26.
State the reaction of nitric acid with alkalis.
Answer:
Reaction of nitric acid with alkalis :
As nitric acid is a strong acid, it rapidly reacts with and neutralises alkali to form salt and water.
Equations :
(a) NaOH + HNO₃ = NaNO₃ + H₂O
(b) NH₄OH + HNO₃ = NH₄NO₃ + H₂O

Question 27.
State the reaction of nitric acid with metals.
Answer:
Reaction of nitric acid with metals :
(i) Reaction with iron : Iron is oxidised to ferric nitrate on reacting with hot concentrated nitric acid.
Equation : Fe + 6HNO₃ = Fe(NO₃)₃ + 3NO₂ + 3H₂O

(ii) Reaction with magnesium :

• Cold and moderately concentrated nitric acid on reaction with magnesium produces magnesium nitrate, nitric oxide and water.
  Equation : 3Mg + 8HNO₃ = 3Mg(NO₃)₂ + 2NO + 4H₂O
• Magnesium liberates hydrogen from cold and very dilute nitric acid.
  Equation : Mg + 2HNO₃ Mg(NO₃)₂ + H₂
• Reaction with copper: Hot concentrated nitric acid reacts with copper metal producing copper nitrate and nitrogen dioxide.
  Equation : Cu + 4HNO₃ = Cu(NO₃)₂ + 2NO₂ + 2H₂O

Question 28.
State the oxidising action of concentrated nitric acid.
Answer:
Oxidising action of concentrated nitric acid :
Cone. HNO₃ is a very good oxidising agent.
It oxidises many metals and non-metals.

(i) Cone. HNO₃ oxidises copper turnings to copper nitrate and itself is reduced to brown coloured nitrogen dioxide gas.

(ii) Concentrated HNO₃ oxidises charcoal i.e. carbon to carbon dioxide and is itself reduced to nitrogen dioxide.

Question 29.
What is passive iron?
Answer:
Passive iron: Cold and concentrated nitric acid or fuming nitric acid when comes in contact with iron produces passive iron. Passive iron is chemically inactive.

Cause if passivity : The nibic acid when comes in contact with iron, an insoluble coating of iron oxide (Fe₃O₄) forms on iron at initial stage. The coating makes iron chemically inactive.

Question 30.
What is aqua regia ? What is its use ?
Answer:
Aqua regia : A mixture of cone. HNO₃ (1 vol.) and cone, hydrochloric acid (3 vols.) is known as aqua regia.

Use of aqua regia : It dissolves gold and platinum.

Question 31.
What is ring test experiment of nitric acid ?
Answer:
Ring test experiment of nitric acid : A little amount of dilute nitric acid is taken in a test tube. Freshly prepared ferrous sulphate is added to it. Now cone. H₂SO₄ is taken in another test tube. cone. H₂SO₄ taken in a tube is carefully poured into the above liquid mixture so as to form a heavy layer at the bottom. A brown ring is formed at the junction of two liquids.

Thus, the reaction involved in ring tests as :

Question 32.
State uses of nitric acid.
Answer:
Uses of nitric acid :

• It is used in the production of explosives such as dynamite, gun cotton, nitro-glycerine, picric acid, and trinitro toluene (TNT).
• It is used to prepare aqua regia in electroplating and in battery.
• It is also used to prepare rayon, artificial silk and dyes.

Question 33.
What is acid rain ?
Answer:
Acid rain The oxides NO₂ and SO₂ reacting with moisture and oxygen of air correspondingly produce HNO₃ and H₂SO₄. The acids dissolve in rain water. The rain coming down on earth carrying these acids is known as acid rain. Function of acid rain : The acids present in the rain water damage buildings monuments, statues by corrosion. Soil also becomes acidic which causes degradation of soil that in turn causes decline in forest area and agricultural productivity.

Question 34.
Sulphuric acid is not prepared directly by adding water to SO₃ why ?
Answer:
Explanation : It is because of the fact that water is not used for absorbing SO₃ as the reaction is exothermic. Result is this that large amount of heat evolved will be a cause of most of SO₃ to be volatilised, the rest amount of it does not form any homogeneous mixture but a dense fog of H₂SO₄ particles is formed. H₂SO₄ is not easily available from the fog. Beside this at high temperature some parts of H₂SO₄ decompose to SO₂ and O₂. Hence water is not directly added to SO₃.

Question 35.
What is fumming sulphuric acid or oleum ?
Answer:
Fumming sulphuric acid or oleum : Fumming sulphuric acid or oleum is obtained when SO₃ is passed over 98% (approximately) sulphuric acid.
Equation:

Question 36.
State the effect of SO₂ pollution
Answer:
of SO₂ pollution ;

• SO₂ creates problems in eyes and also in lungs,
• Many diseases like asthama, bronchitis etc. effect if SO₂ is inhaled.

Question 37.
Historical monuments like Tajmahal is also affected by sulphuric acid – why ?
Answer:
Reason : Historical monuments like Tajmahal are damaged due to corrosion when rain carrying H₂SO₄ acid pour on these. Environmentalists say the corrosion of Tajmahal is due to presence of SO₂ in high concentration in the air of Agra. The SO₂ gas emitted from petroleum refinery situated on the other side of the Jamuna river reacts with oxygen and moisture of air to produce H₂SO₄.

Question 38.
What are possible remedies to save our historical monument—Tajmahal?
Answer:
Possible remedy :

• Banning of this factories in the neighbourhood region of Taj and also in Mothura is promulgated by an ordinance.
• Excessive use of motor vehicles should be restricted. Petroleum refining plant should be kept 90 km apart.
• Electrostatic precipitators which are used for treatment of the harmful emitted gas S0₂ before emission.

Question 39.
What is stone cancer ?
Answer:
Stone cancer : In atmosphere, Sulphur dioxide (SO₂) gas reacts with oxygen and water vapour producing sulphuric acid. The acid being dissolved in rain water comes down on marble walls. The marble walls thus corrode, the corrosion of the marble is called stone cancer.

Question 40.
State physical properties of H₂SO₄.
Answer:
Physical properties of H₂SO₄ :

• It is colourless, odourless heavy oily liquid.
• Its specific gravity is 1.84 and its b.p. (boiling point) is 338°C.
• It is soluble in water and it is a corrosive acid.

Question 41.
Water is not added on concentrated sulphuric acid to make it dilute — why ?
Answer:
Explanation : Huge amount of heat is produced if water is added to con­centrated sulphuric acid. As a result water all on a sudden being volatilised spreads all around and creates problem. So, cone. H₂SO₄ acid is slowly added to with constant stirring.

Question 42.
State the reaction of H₂SO₄ with alkalis.
Answer:
Reaction of H₂SO₄ with alkalis : As H₂SO₄ is a dibasic acid containing two replaceable hydrogen atoms, it reacts with bases and alkalis to produce two types of salts acid salts and normal salts and water.
Equation :

Question 43.
State the reaction of H₂SO₄ with carbonates and bicarbonates.
Answer:
Reaction of H₂SO₄ with carbonates and bicarbonates : At ordinary temperature it liberates carbon dioxide from carbonates and bicarbonates.
Equation :

Question 44.
State the reaction of H₂SO₄ with metals.
Answer:
Reaction of H₂SO₄ with metals :
Metals lying above hydrogen in the electrochemical series react with dilute sulphuric acid to form hydrogen gas.
Equation :
(a) Mg + H₂SO₄ = MgSO₄ + H₂↑
(b) Zn + H₂SO₄ = ZnSO₄ + H₂↑

Question 45.
State the oxidising property of concentrated sulphuric acid.
Answer:
Oxidising property of concentrated sulphuric acid :
(a) Reaction with metals : Hot and concentrated sulphuric acid oxidises metallic copper, silver, zinc etc. into their sulphates, itself being reduced to sulphur dioxide.
Equation :

(b) Reaction with non-metals Non-metals carbon and sulphur on being treated with hot concentrated sulphuric acid are oxidised to carbon dioxide, sulphur dioxide respectively.
Equation :

Question 46.
State the dehydration action of concentrated sulphuric acid.
Answer:
Dehydration action of concentrated sulphuric acid :
(a) Concentrated sulphuric acid chars sugar. The acid takes up all its hydrogen and oxygen in the form of water molecules from the compound separating black carbon as residue.
Equation :

(b) When a mixture of formic acid and concentrated sulphuric acid is heated carbon monoxide is produced by loss of water molecule from the formic acid.

Equation

Question 47.
What is the identification reaction of sulphuric acid ?
Answer:
Identification reaction of sulphuric acid : When barium chloride solution is added to dilute sulphuric acid, a white precipitate of barium sulphate insoluble in dilute or concentrated hydrochloric acid or nitric acid is obtained.
Equation :

Question 48.
State the uses of sulphuric acid.
Answer:
Uses of sulphuric acid :

• It is used for the preparation of different chemical compounds like HCl, HNO₃, ether, alcohol etc.
• It is used as an important raw material for dyes, medicine, plastic industries.
• It is used to prepare different explosives like trinitrotoluene (TNT) nitroglecer- ine etc.

Question 49.
Explain the following :
Concentrated nitric acid turns yellow in sun light.
Answer:
Explanation Nitric acid turns yellow because of its decomposition forming nitrogen dioxide (NO₂gas.
Equation : 4HNO₃= 4NO₂+ 2H₂O + O₂

Broad Answer Type Questions

Question 1.
State the contact process for the manufacture of sulphuric acid.
Answer:
Contact process for the manufacture of sulphuric acid :
Principle : (a) Formation of SO₂: SO₂ is prepared by burning sulphur or iron pyrites in excess of air.

(b) Formation of Sulphur trioxide (SO₃) SO₃ is prepared by the oxidation of sulphur dioxide with oxygen (from air) in presence of platinised asbestos or, V₂O₅ as catalyst at 450°C.
Equation:

(c) Formation of oleum : Now sulphur trioxide thus produced are not allowed to react with water directly. Sulphur trioxide absorbs concentrated sulphuric acid (98%) turning it as fumming sulphuric acid or oleum.
Equation :

(d) Dilution of oleum to sulphuric acid : Pure and concentrated sulphuric acid is produced by adding slowly requisite amount of water in fumming sulphuric acid.
Equation : H₂S₂O₇ + H₂O = 2H₂SO₄

Question 2.
State an experiment to illustrate the solubility of HCl in water and the acidic character of the aqueous solution.
Answer:
Fountain experiment : A round bottomed flask is fitted with a cork through which passes a long tube ending in a jet in­side the flask. The flask is filled with hydrogen chloride and clamped in an inverted position so that the other end of the tube dips in water coloured blue by litmus.

The flask is then cooled when the gas contracts inside. As a result, the blue solution rises up through the tube and enters the flask in the form of fountain. The blue litmus solution in the flask turns red. This experiment proves simultaneously the solubility of hydrogen chloride in water and the acidic character of its aqueous solution.