WBBSE Class 10 Physical Science Solutions Chapter 8.5 Metallurgy

Detailed explanations in West Bengal Board Class 10 Physical Science Book Solutions Chapter 8.5 Metallurgy offer valuable context and analysis.

WBBSE Class 10 Physical Science Chapter 8.5 Questionuestion Answer – 8.5 Metallurgy

Very Short Answer Type Questions

Question 1.
Which metal is present in the earth’s crust in largest percentage ?
Answer:
Aluminium.

Question 2.
What is stainless steel ?
Answer:
Stainless steel is an alloy of iron with chromium and nickel.

Question 3.
What is the purpose of galvanising an article ?
Answer:
The purpose of galvanising an article to protect the article from corrosion.

Question 4.
What is the action of alkali on iron ?
Answer:
Iron does not react with any alkali.

Question 5.
How hydrogen gas may be prepared using aluminium ?
Answer:
Hydrogen gas may be prepared by boiling aluminium powder with alkali.

Question 6.
What is the basic component of chuni (ruby), panna (emarald) etc.?
Answer:
The basic component of chuni and panna is Al₂O₃.

Question 7.
What is an ore ?
Answer:
Ores are the minerals from which the metals can be extracted conveniently and profitably.

Question 8.
Name a metal that reacts both with an acid and alkali to produce salt and hydrogen.
Answer:
Zinc or Aluminium.

Question 9.
Name the chief ore of Zinc and write down its formula.
Answer:
The chief ore of Zinc is Zinc blende. Formula of zinc blende ZnS

Question 10.
Burning of which metal cannot be extinguished with CO₂ gas ?
Answer:
Burning of magnesium cannot be extinguished with CO₂ gas.

Question 11.
Which metals are present in brass ?
Answer:
Copper and Zinc are present in brass.

Question 12.
Name an alloy of magnesium.
Answer:
Electron is an alloy of magnesium.

Question 13.
Which type of iron is used in the core of an electromagnet ?
Answer:
Soft iron is used in the core of an electromagnet.

Question 14.
Which metal is commonly used for galvanisation ?
Answer:
Zinc is commonly used for galvanisation.

Question 15.
Name a metal that produces amphotaric oxide.
Answer:
Aluminium or Zinc produces amphoteric oxide.

Question 16.
Name two metals which do not react with alkali.
Answer:
Copper, iron do not react with alkali.

Question 17.
Which metal can produce hydrogen from dilute nitric acid ?
Answer:
Magnesium can produce hydrogen from dilute nitric acid.

Question 18.
Name the chief ore of magnesium.
Answer:
The chief ore of magnesium is Magnesite (MgCO_s).

Question 19.
Name the principle ore of aluminium.
Answer:
The principle ore of aluminium is Bauxite (Al₂O₃, 2H₂O),

Question 20.
Name two alloys of aluminium.
Answer:
Two alloys of aluminium are :

• Duralumin
• Aluminium bronze

Question 21.
What is metallurgy ?
Answer:
Metallurgy is the process of extracting metals from their ores.

Question 22.
What is gangue ?
Answer:
Gangue or matrix are the rocky and earthly impurities associated with the minerals.

Question 23.
What is slag ?
Answer:
Slag is the light and fusible material obtained by the combination of flux with gangue.

Question 24.
What is Flux ?
Answer:
Flux is the substance which combines with gangue to form light and easily fusible material called slag.

Question 25.
What is thermite ?
Answer:
Thermite is the mixture of metal oxide and the aluminium powder.

Question 26.
What is amalgamation ?
Answer:
Amalgamation is the process in which finely powdered ore is brought into contact with mercury which combines in the ore to form amalgam.

Question 27.
Why alkali metals are not found in free state in nature ?
Answer:
Due to high reactivity, alkali metals do not occur free in nature.

Question 28.
What is called fusion mixture ?
Answer:
A mixture of Na₂CO₃ and K₂CO₃ is called fusion mixture.

Question 29.
What is Black ash ?
Answer:
Mixture of Na₂CO₃ and CaS is called black ash.

Question 30.
What is Lime light ?
Answer:
On heating in oxy-hydrogen flame, lime becomes incandescent and emits bright white light, called lime light.

Question 31.
What is American baking powder ?
Answer:
Pure Ca(H₂PO₄)₂ is used as American baking powder.

Question 32.
What is the use of MgSO₄, 7H₂O?
Answer:
MgSO₄, 7H₂O is used as a purgative in medicine.

Question 33.
What is Hydrolith ?
Answer:
Calcium hydride is known as hydrolith.

Question 34.
What is the constituent of bones and teeth ?
Answer:
Calcium phosphate is the constituent of bones and teeth.

Question 35.
What is the most abundant metal next to aluminium ?
Answer:
Iron is the most abundant metal, next to aluminium.

Question 36.
What is Cementite ?
Answer:
Iron carbide (Fe₃C) is known as cementite.

Question 37.
What is Green vitriol ?
Answer:
FeSO₄,7H₂O is called green vitriol.

Question 38.
What is called Mohr’s salt ?
Answer:
FeSO₄,(NH₄)₂SO₄, 6H₂O is called Mohr’s salt.

Question 39.
What is Kipp’s base ?
Answer:
Mixture of FeS + H₂SO₄ is called Kipp’s base.

Question 40.
What is Invar ?
Answer:
Invar is an alloy of steel containing 36% nickel.

Question 41.
What is Spiegeleisen ?
Answer:
Spiegeleisen is an alloy of iron, manganese and carbon used in steel making.

Question 42.
What is Matte ?
Answer:
Matte contains Cu₂S + FeS.

Question 43.
What is Blister Copper ?
Answer:
Blister Copper contains (96 -98)% copper with small amounts of Ag and Au as impurity.

Question 44.
What is called Fool’s gold ?
Answer:
CuFeS₂ is called Fool’s gold.

Question 45.
What Nila thotha ?
Answer:
Blue vitriol (CuSO₄, 5H₂O) is called ‘Nila thotha’.

Question 46.
What is Bordeaux mixture?
Answer:
Mixture of CuSO₄ solution and lime called Bordeaux mixture is used as fungicide.

Question 47.
What is Philosopher’s wool ?
Answer:
Zinc oxide is called philosopher’s wool, zinc white or Chinese white.

Question 48.
What is the nature of ZnO ?
Answer:
ZnO being amphoteric in nature dissolves both in acids and alkalis.

Question 49.
What is Lithopone ?
Answer:
Lithopone (ZnS + BaSO₄) is used as white paint.

Question 50.
What is the use of ZnS ?
Answer:
ZnS is used for preparing luminous dials for watches and X-ray screens.

Question 51.
What is German silver ?
Answer:
German silver is an alloy of Cu (60%), Zn (20%) and Ni (20%). It does not contain silver.

Question 52.
What is White vitriol ?
Answer:
Zinc sulphate hepta hydrate (ZnSO₄, 7H₂O) is called white vitriol

Question 53.
Which metal is common in both bell metal and bronze?
Answer:
Bell metal and bronze are both allloys of copper and tin.

Question 54.
What is the non metallic component present in stainless steel?
Answer:
The non-metallic component of stainless steel is carbon (c).

Question 55.
What is the reason behind Wilson’s disease?
Answer:
This occurs due to abnormal metabolism of copper and as a result, free copper in the plasma enters different tissues, binds with proteins and gets deposited in liver, kidney and brain.

Question 56.
Write the chemical reaction involved in thermite process.
Answer:
The chemical reaction involved is as follows :
Fe₂O₃ + 2Al → 2Fe + Al₂O₃ + heat

Question 57.
What is anodizing ?
Answer:
Anodizing is a process by which a thick, protective layer of aluminium oxide is applied on the aluminium metal surface to protect it from corrosion.

Question 58.
Why does a new aluminium vessel lose its shine?
Answer:
In presence of air, a thin layer of aluminium oxide is formed on the surface of metallic aluminium. So, the aluminium vessel loses its shine.
4Al + 3O₂ = 2Al₂O₃

Question 59.
What is the principle behind extracting less reactive metals?
Answer:
Metals with less reactivity are extracted by heating their oxides.

Question 60.
What is the principle behind extracting highly reactive metals?
Answer:
Metals of high reactivity are extracted by the electrolytic reduction of their molten chlorides or oxides. During electrolysis, the pure metal is produced at the cathode.

Question 61.
What is the principle behind extracting moderately reactive metals?
Answer:
Metals which are moderately reactive are extracted by reduction of their oxides with carbon (or zinc or iron etc.)

Question 62.
Rusting is a redox process. What is the oxidation reaction?
Answer:
The oxidation process is the oxidation of metallic ion to Fe²⁺ and finallly to Fe³⁺ ion occurring at the anode.

Short Answer Type Questions:

Question 1.
Concentrate Nitric acid can be kept in vessel made of aluminium why?
Answer:
Reason Concentrate Nitric acid does not react with aluminium, so it can be kept in aluminium vessel.

Question 2.
Should we take or not ‘pickle’ wrapped to aluminium foils ?Give reasons.
Answer:
Reason : Pickle contain organic acetic acid known as vinegar, which reacts with aluminium foil to produce aluminium salts which are harmful to our health. So pickle’s wrapped in aluminium foils should be taken.

Question 3.
What happens when a spoon made of iron is introduced in acidified CuSO₄ solution ?
Answer:
Explanation : Spoon made of iron reacts with acidified CuSO₄ solution precipitation metallic copper and blue copper sulphate solution turns green due to formation of ferrous sulphate.
Equation : CuSO₄ + Fe = FeSO₄ + Cu↓

Question 4.
In the burning of magnesium carbon-dioxide is not used as a fire ex­tinguisher why ?
Answer:
Explanation : Burning Magnesium produces heat which breaks carbon dioxide to carbon and oxygen. This oxygen enhance magnesium burning. SO₂, CO₂ is not used to extinguish magnesium burning.
Equation : Mg + CO₂ = MgO + C

Question 5.
Rain damages lajmahal. Do you agree ? Give reason.
Answer:
Reason : Rain water contains nitric acid. The nitric acid is formed by natural ways in the following manner. Nitrogen reacts with oxygen, both present in v air, by thunder to form nitric oxide. Nitric oxide further reacts with oxygen to form nitrogen dioxide.

Nitrogen dioxide dissolves in rain water to produce nitric acid. Tajmahal is made of lime stone i.e. Calcium carbonate (CaCO₃). Nitric acid (HNO₃) reacts with CaCO₃ to form Ca(NO₃)₂. Thus rain damages Tajmahal.
Equation : CaCO₃ + 2HNO₃ = Ca(NO₃)₂ + CO₂+ H₂O

Question 6.
What is Thermite ? What is its use ?
Answer:
Thermite : Thermite is a mixture of aluminium powder and ferric oxide.
Use : It is used for welding purposes.

Question 7.
State what happens when :
Zn is added to caustic soda solution
Answer:
Explanation : Zinc reacting with caustic soda solution produces sodium zincate and hydrogen gas.
Equation : Zn + 2NaOH = Na₂ZnO₂ + H₂↑

Question 8.
State what happens when :
Steam is passed over red hot iron.
Answer:
Explanation : When steam is passed over red-hot iron (600°C – 800°C), hydrogen is set free and iron is oxidised to ferrosoferric oxide.
Equation : 3Fe + 4H₂O = Fe₃O₄ + 4H₂↑

Question 9.
State what happens when :
Steam is passed over red hot zinc.
Answer:
Explanation : When steam is passed over red hot zinc, zinc oxide and hydrogen gas form.
Equation : Zn + H₂O= ZnO + H₂↑

Question 10.
What compounds are formed when magnesium is burnt in air ?
Answer:
Explanation : Magnesium oxide (MgO) and magnesium nitride (Mg₃N₂) are formed when magnesium is burnt in air.
Equation :
(a) 2Mg + O₂ = 2MgO
(b) 3Mg + N₂ = Mg₃N₂

Question 11.
What is Galvanisation ? State one use of Zinc.
Answer:
Galvanisation : It is a process of coating an article with zinc. The purpose of galvanisation an article is to protect it from corrosion. Iron articles are galvanised to protect the articles from rusting.
Use of Zinc : Zinc is largely used to prepare zinc white, a paint.

Question 12.
‘All ores are minerals but all minerals are not ores’ — Explain.
Answer:
Explanation : Compounds of a metal which exist in combination with similar compounds of other metals are known as minerals. A metal may occur in many minerals. The particular mineral from which a metal may be conveniently and eco­nomically extracted is called the ore of the metal.

Question 13.
What is Stainless steel ? State one use of it.
Answer:
Stainless steel : It is an alloy which composes Iron (Fe) = 73%, Chro­mium (Cr) = 18% and Nickel (Ni) = 8% and Carbon (C)
Uses of stainless steel : It is broadly used to make instruments.

Question 14.
What is Philosopher’s wool ?
Answer:
Philosopher’s wool : Zinc oxide is called philosopher’s wool, zinc white or Chinese white. It is a white powder which becomes yellow on heating and again becomes white on cooling. It is used as a white fluorescent paint because it is not darkened by hydrogen sulphide.

Question 15.
What is an alloy? Name one alloy.
Answer:
Alloy : An alloy is a homogeneous mixture (or, sometimes a heterogeneous combination) of two or more metals, behaving as a single metal in most of its physical properties.
Example : Bronze (Cu : 90% ; Sn : 10%)

Question 16.
State the advantages of an alloy over pure metal.
Answer:
Advantages of an alloy over pure metals :

• Increase of hardness.
• Increase in resistance to corrosion.
• Increase in fusibility or decrease in melting point.
• Improvement of casting property.

Question 17.
Two metals A and B produce hydrogen when react with hot NaOH solution. A does not react with H₂SO₄ but B produces a salt and hy­drogen gas reacting with H₂SO₄ Identify A and B.
Answer:
Identification : The metal A is aluminium and the metal B is zinc both of which react with hot NaOH solution to produce hydrogen.

Aluminium does not react with H₂SO₄ but zinc reacts with H₂SO₄ to produce salt and hydrogen.
Equation : Zn + H₂SO₄ = ZnSO, + H₂↑

Question 18.
What is the difference between mineral and ore of a metal ?
Answer:
Difference between mineral and ore of a metal :

Mineral	Ore
Compounds of a metal which exist in combination with similar compounds of other metals are known as minerals A metal may occur in many minerals.	The particular mineral from which a metal may be conveniently and economically extracted is called the ore of the metal.

Question 19.
Why alumina (Al₂O₃)cannot be reduced by carbon ?
Answer:
Explanation At high temperature, Al₂O₃ reacts with carbon to form alu­minium carbide.
Equation : \(2 \mathrm{Al}_2 \mathrm{O}_3+9 \mathrm{C} \rightleftharpoons \mathrm{Al}_4 \mathrm{C}_3+6 \mathrm{CO}\)

Question 20.
Why aluminium cannot be obtained by the electrolysis of fused AlCl₃?
Answer:
Explanation Aluminium cannot be obtained by the electrolysis of fused AlCl₃ since it is covalent solid and sublimes at 453K.

Question 21.
Although less conducting than copper, aluminium is used for power transmission. Why ?
Answer:
Explanation : Aluminium being lighter and cheaper than copper is used for power transmission.

Question 22.
What is the role of cryolite (Na₃AlF₆) in the electro-chemical reduc­tion of Al₂O₃ during the preparation of aluminium ?
Answer:
Explanation : Cryolite (Na₃AlF₆) is added to alumina ;

• to decrease its melting point from 2273K to 1173K.
• to increase its electrical conductivity.

Question 23.
Why aluminium acts as a good reducing agent ?
Answer:
Explanation : Reducing character of a substance depends upon its affinity for oxygen. Aluminium due to its high affinity for oxygen is a good reducing agent. It reduces a large number of oxides of other metals. e.g. 2Al + Fe₂O = Al₂O₃ + 2fe + heat.

Question 24.
Give reasons for the following:
Although aluminium is above hydrogen in electrochemical series, it is stable in air and water.
Answer:
Explanation : Aluminium reacts readily with air and water and a thin layer of its oxide gets deposited on its surface. This oxide coating protects the underlying metal from further action.

Question 25.
Aluminium containers can be used to store cone. HNO₃
Answer:
Explanation : Aluminium on treatment formation of a protective coating of its oxide. Thus aluminium containers can be used to transport cone. HNO₃

Question 26.
Finely powdered aluminium on exposure to air becomes hazadous. Why
Answer:
Explanation : Aluminium due to its great affinity for oxygen forms Al₂O₃ and the reaction is highly exothermic. Finely divided aluminium powder due to its large surface area, reacts vigorously with air and is hazardous.

Question 27.
Explain the following :
Anode mud in copper refining contains silver and gold.
Answer:
Explanation Silver and gold being less electropositive than copper are not ionised under the applied voltage and get deposited in the anode mud.

Question 28.
Explain the following :
Copper metal is largely used to make electrical cables.
Answer:
Explanation : Copper mainly used in making electrical cables because it is a good conductor. Moreover, being a noble metal, it is not affected by the atmosphere.

Question 29.
In moist air, copper corrodes to produce a green layer on the surface. Explain.
Answer:
Explanation : In presence of moist air, a thin layer of green basic copper carbonate is formed on the surface of copper leading to its corrosion.

Question 30.
Copper salts are coloured where as Zinc salts are colourless. Why
Answer:
Reason Copper salts are coloured because of the presence of an unpaired electron in Cu²⁺. This electron absorbs radiations of orange colour from white light for excitation from one energy level to another with the same d-subs shell. Hence, transmitted light appears blue. On the other hand, zinc salts are white because of the absence of vacant orbitals to which the electrons can be excited.

Question 31.
Explain why lime stone is used in the manufacture of pig iron from haematite.
Answer:
Explanation On heatingTime stone decomposes to give CaO which then combines with silica to form slag. Equation :
(a) CaCO₂ \(\rightleftharpoons\) CaO + CO₂
(b) SiO₂ + CaO = CaSiO₃ (slag)

Question 32.
What is the difference between cast iron. wrought iron and steel?
Answer:
Explanation The three forms differ in the percentage of carbon. Cast iron contains (2 -4-5)% carbon, wrought iron contains about 0-25% carbon, while steel contains (0T-T5)% carbon.

Question 33.
What is amalgam? Give example!
Answer:
Amalgam : If one of the components of an alloy is mercury then this alloy.

Broad Answer Type Questions

Question 1.
State the following:
(i) Chief one
(ii) Important properties and equations
(iii) Uses of:
(a) Aluminium
(b) Copper
(c) Iron
(d) Magnesium
(e) Zinc.
Answer:
List of chief ore, propetites, uses of Al, Cu, Fe, Mg, Zn :

Question 2.
State some alloy. with their composition and use :
Answer:
Common alloys of Al, Mg, Zn