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METALS

CHAPTER-15

METALS

Text Book Question and Answers

I. Four alternatives are given to each of the incomplete statements/questions. Choose the answer
1. The following is a metal in liquid state at room temperature
(a)Bromine (b)Mercury (c)Germanium (d)Silicon
Answer: (b)Mercury
2. The following element forms cations.
(a)Sulphur (b)Graphite (c)Manganese (d)Iodine
Answer: (c)Manganese
3. The oxide that can form salt and water with a base as well as with an acid is,
(a)Carbon monoxide (b)Sulphur dioxide (c)Sodium Oxide (d)Aluminium oxide.
Answer: (d)Aluminium oxide.
4. Electron donor among the following is,
(a)Potassium (b)Phosphorus (c)Oxygen (d)Fluorine
Answer: (b)Phosphorus
5. Hydrogen gas is liberated under the following circumstance.
(a)iron kept in boiling water (b)water is poured on hot iron
(c)Steam is passed over red hot red (d)Iron is immersed in cold water.
Answer: (c)Steam is passed over red hot red
6. The metal that cannot liberate hydrogen with dilute acids is,
(a)Sodium (b)Aluminium (c)Copper (d)Potassium
Answer: (c)Copper
7. Lemon juice is served normally in ceramics or glass tumblers instead of metallic tumblers because,
(a)glass and ceramics (b)metallic containers react with the acids of lemon
(c)lemon juice produces combustible hydrogen gas with metallic tumblers
(d)glass and ceramics keep the lemon juice cooler
Answer: (b)metallic containers react with the acids of lemon
8. The following combination of metal and acid liberate sulphur dioxide
(a)Zinc and dilute Nitric acid (b)Zinc and dilute Sulphuric acid
(c)Zinc and Hydrochloric acid (d)Zinc and concentrated Sulphuric acid.
Answer: (d)Zinc and concentrated Sulphuric acid.

II. Fill in the blanks
1. Cu + 2H2SO4 ------> CuSO4 + 2H2O + SO2
2. 2Na + 2H2O -------> 2NaOH + H2
3. The alloy that has least coefficient of linear expansion is Invar
4. Germanium is purified by the technique Zone refining or fractional crystallization
5. Reducing agent used in the extraction of iron is Coke
III. State whether the following statements are true or false
1. Gold occurs in native form - True
2. Sodium is always found in compound state - False
3. Mercury can displace hydrogen from dilute acids - False
4. Ornamental gold is not an alloy - False
5. Iron becomes passive when immersed in concentrated nitric acid - True
IV. Match the following
1. Haematite - Oxide
2. Copper pyrites - Sulphate
3. Limestone - Carbonate
4. Common salt – Chloride
V. Give reasons for the following
1. Magnesium ribbon should not be kept near bottles containing volatile chemicals.
Magnesium is highly reactive hence it should not be placed near bottles with volatile chemicals.
2. Aluminium becomes passive when dipped in concentrated nitric acid.
Aluminium becomes passive when dipped in concentrated nitric acid due to the formation of protective oxide layer on the metal instantly.
3. Limestone and coke are used in the extraction of Iron form Haematite.
Limestone helps in the removal of silica from the ore in the form of calcium silicate slag. Coke is used as it is a cheaper reducing agent.
4. Nitric acid is not normally used to prepare hydrogen gas in the laboratory.
Nitric acid has to be diluted to a great extent as it is a good oxidizing agent hence it is not normally used
5. Aluminium cannot be extracted by heating bauxite and coke.
This is because oxygen of aluminium oxide cannot be easily taken away by reducing agents like coke as aluminium has greater affinity towards oxygen.
6. Tin is used to coat the inner walls of brass and copper utensils.
Coating brass and copper utensils with tin avoids oxidation of brass and copper.
VI. Answer the following questions
1. Name any two ores of Iron
i. Haematite ii. Magnetite
2. Name the constituents of the alloy stainless steel.
The constituent are Iron, Carbon, Chromium and Nickel.
3. Name any three methods of refining a metal
The methods of refining a metal are
i. Fractional crystallization or zone refining
ii. Vacuum melting
iii. Chemical vapour deposition
iv. Liquation process
v. Electrolytic refining
4. Write a neat diagram of blast furnace and label the parts.
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5. Write balanced equation of the reaction taking place between copper and moderately concentrated nitric acid when heated.
Copper + moderately diluted nitric acid ---> copper nitrate + nitric oxide + water.
3Cu + 8HNO3 ---> 3Cu(NO3)2 + 2NO + 4H2O
6. Draw a neat diagram of the apparatus used in the extraction of aluminium from bauxite and label the parts.
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Additional Questions

1. Distinguish between a metal and a non metal in physical properties.

MetalNon metal
Solids at room temperatureOccur in all the three states namely, solid, liquid and gaseous state
SonorousNon sonorous
Generally malleable and ductileBrittle
Generally conduct electricity conductivity differs from metal to metalDo not conduct electricity
Generally conduct heatDo not conduct heat
LustrousNon lustrous

2. Distinguish between a metal and non metal in chemical properties
MetalNon metal
Electron donors and hence electropositiveElectron acceptors and hence electronegative
Generally form ionic bondGenerally form both ionic and covalent bond
Generally displace hydrogen form dilute acidsDo not displace hydrogen from dilute acids
Aqueous solutions of metallic oxides turn red litmus blue. Metallic oxides are basic, oxides of zinc and aluminium are amphoteric in the sense that they form salt and water with a base as well as with an acid.Aqueous solutions of non-metallic oxides turn blue litmus red. Non-metallic oxides are acidic. Non-metallic oxides such as nitrous oxides, carbon monoxide are neutral oxides. They do not dissolve in water.
Some oxides of metals in aqueous solution react with zinc to produce hydrogenAqueous solutions of oxides of non-metals react with carbonates producing carbon dioxide.

3. Write the action of other non metals on metals.
a) 3Mg(magnesium) + N2 (Nitrides) ----> Mg3N2 (Magnesium nitride)
b) Ca (Calcium) + H2(Hydrogen) ---> CaH2(calcium hydride)
c) 2Al(Aluminium) + 3Cl2(Chlorine) ----> 2AlCl3 (Aluminium Chloride)
d) Fe(Ferrous) + S(Sulphur) ---> FeS (Ferrous sulphide)
4. Write the action of concentrated sulphuric acid on metals
a) Cu + 2H2SO4 ----> CuSO4 + SO2 + 2H2O
b) Zn + 2H2SO4 ----> ZnSO4 + SO2 + 2H2O
5. Write the action of very dilute nitric acid on metals.
Very dilute nitric acid reacts with magnesium metals to liberate hydrogen gas
Mg + 2HNO3 ---> Mg(NO3)2 + H2
Copper + moderately diluted nitric acid ----> copper nitrate + nitric oxide + water.
3Cu + 8HNO3 -----> 3Cu(NO3)2 + 2NO + 4H2O
Copper + concentrated nitric acid -----> copper nitrate + nitrogen dioxide + water.
Cu + 4HNO3 ------> Cu(NO3)2 + 2NO2 + H2O
6. Write the displacement reaction of metals.
CuSO4 + Fe -----> FeSO4 + Cu
7. Name the metals that are available in Free State in nature.
i. Gold ii. Silver iii. Platinum
8. Name the oxide ores, sulphide ores and carbonate ores
Oxide ores – Bauxite, Haematite, Limonite, Magnetite and cuprite.
Sulphide ores – Copper glance, Copper pyrites or Chalco pyrites and Iron pyrites.
Carbonate ores – Siderite, Azurite, Malachite and lime stone.
9. List the metallic ores of Karnataka
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10. Define the following (a)Metallurgy (b) gangue (c) Roasting (d) calcination (e)Concentration of the ore. (f) Flux.
(a)Metallurgy: The technology of extraction of metals from their ores and refining to the required from is metallurgy
(b)gangue: The unwanted impurities present in the ore are called gangue particles.
(c)Roasting: Roasting is the process of heating the ore just below its melting point in the presence of air.
(d)Calcination: Calcination is a process of heating the ore just below its melting point in the absence of air.
(e)Concentration of the ore: It is a process of concentrated by removing unwanted impurities.
(f)Flux: Flux is a substance that is added to the ores before heating with a purpose of removing certain unwanted impurities which are not removed during the concentration of ore.
11. Define Slag
Flux combines with the impurities and forms a compound called slag.
12. What is pig iron? Name the other name of pig iron.
The molten iron is converted into solid blocks called pig iron. Other name of pig iron is cast iron.
13. What is an alloy?
Alloy is a homogeneous mixture of (a) two or more metals, or (b) metals and non-metals in suitable proportion.
14. Write the constituents of commonly used alloys
image

15. Draw neat diagram of Electrolytic refining of copper and label the parts.
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16. What is the action of the following metals with oxygen of air? Write the equations.
a) Sodium b) Copper c) Magnesium d)Aluminium
Metals generally react with different components of the air. Different metals react in different ways under different conditions. They react with oxygen of air to produce their respective oxides.
a) Sodium: Sodium reacts with the component of air gradually to produce sodium carbonate.
4Na + O2 ®2Na2O
Na2O + CO2 ®Na2CO3
When sodium burns in excess of oxygen, it produces sodium peroxide
2Na + O2 ®Na2O2
b) Copper: Copper reacts with the air to produce is an oxide of copper.
2Cu + O® 2CuO
c) Magnesium: Magnesium reacts with the air to produced magnesium oxide.
2Mg + O2 ®2MgO
d) Aluminium: Aluminium reacts with the air to produced aluminium oxide
4Al + 3O2 ----> 2Al2O3
17. Which compound to require for iron to rust?
Air and Water are required for iron to rust.
18. What is rust? Write its chemical formula.
The rust is hydrated oxide of iron. The chemical formula of rust is Fe2O32H2O.
19. How to Iron is protected from rust.
Iron is protected from rusting by coating it with zinc or by painting it. Iron pipes are protected by heating and then dipping them in molten coal tar.
20. What is the action of the following metals with water? Write the equations.
a) Sodium b) Zinc c) Magnesium d) Iron
When metals react with water, hydrogen is liberated.
a) Sodium: Sodium Metal reacts with water to produced sodium hydroxide and hydrogen gas.
2Na + 2H2O ®2NaOH + H2­
b) Zinc: Zinc metal reacts with water to produced zinc oxide and hydrogen gas.
Zn + H2O ®ZnO + H2­
c) Magnesium: Magnesium metal reacts with water to produced magnesium oxide and hydrogen gas.
Mg + H2O®MgO + H2­
d) Iron: Iron is reacts with water to produced Ferric oxide and hydrogen gas.
3Fe + 4H2O®Fe3O4 + 4H2­
21. What is the action of the following metals with dilute hydrochloric acid? Write the equations.
a) Zinc b) magnesium c) iron
Metals react with dilute hydrochloric acid to produce hydrogen with the formation of their respective metallic chlorides.
a) Zinc: Zinc metals react with dilute hydrochloric acid to produce zinc chloride and hydrogen gas.
Zn + 2HCl ®ZnCl2 + H2 ­
b) Magnesium: Magnesium metals react with dilute hydrochloric acid to produce Magnesium chloride and hydrogen gas.
Mg + 2HCl ® MgCl2 + H2 ­
c) Iron: Iron metals react with dilute hydrochloric acid to produce Ferric chloride and hydrogen gas.
2Fe + 6HCl ®2 FeCl3 + 3H2­
22. What is the action of the following metals with dilute sulphuric acid? Write the equations.
a) Zinc b) magnesium c) iron
Metals react with dilute sulphuric acid to produce hydrogen with the formation of their respective metallic sulphates.
a) Zinc: Zinc metals react with dilute sulphuric acid to produce zinc sulphate and hydrogen gas.
Zn + H2SO4 ®ZnSO4 + H2­
b) Magnesium: Magnesium metals react with dilute sulphuric acid to produce Magnesium sulphate and hydrogen gas.
Mg + H2SO4 ®Mg SO4 + H2­
c) Iron: Iron metals react with dilute sulphuric acid to produce Ferric sulphate and hydrogen gas.
Fe + H2SO4 ®Fe SO4 + H2­
23. What is the action of the following metals with nitric acid? Write the equations.
a) Zinc b) magnesium c) copper
Metals react with nitric acid to produce hydrogen with the formation of their respective metallic nitrates.
Zn + 2HNO3 ®Zn (NO3)2 + H2­
Mg + 2HNO3 ®Mg (NO3)2 + H2­
Metals produce nitrates and nitric oxide with moderately concentrated nitric acid.
3Cu + 8 HNO3 ®3 Cu ((NO3)2 + 2NO + 4H2O
Metals produce metallic nitrates and nitrogen dioxide with concentrated nitric acid.
Cu + 4HNO3 ®Cu (NO3)2 + 2NO2­+ 2H2O
Copper produces cupric nitrate with nitric acid.
24. What is the action of the following metals with chlorine? Write the equations.
a) Aluminium b) Iron c) copper
Metals react with chlorine to form of their respective metallic chlorides.
2Al + 3Cl2 ®2AlCl3.
2Fe + 3Cl2 ®2FeCl3
Cu + Cl2 ®CuCl2
25. Identify the group and period of those metals in the periodic table.
a) Copper b) iron
a) Copper – 11th groups, 4th period.
b) Iron – 8th groups, 4th period.
26. Write the atomic number, mass number, symbol and electronic configuration, of a copper atom.
Atomic number- 29
Mass number – 64
Symbol – Cu
Electronic configuration – 1s22s22p63s23p63d104s1
27. Write the atomic number, mass number, symbol and electronic configuration of an iron atom.
Atomic number- 26
Mass number – 56
Symbol – Fe
Electronic configuration – 1s22s22p63s23p63d64s2
28. Name the ores of copper.
The chief ore of copper is copper pyrites (CuFeS2). The other ores are copper glance (Cu2S), Cuprite (Cu2O), malachite [CuCO3Cu(OH)2] and azurite [2CuCO3Cu(OH)2]
29. Name the ores of iron.
The ores of iron are: haematite (Fe2O3), magnetite (Fe3O4), limonite (Fe2O3 H2O) and siderite (FeCO3).
30. Explain the method of concentration of copper ore.
The finely powdered ore is mixed with pine oil and water in a large tank. The sulphide ore mixes with oil and forms a thin film. Oil does not have affinity for earthly materials. The materials other than the ore particles are wetted by water. When air is bubbled through the mixture, froth containing the particles of copper ore floats on top of water and can be skimmed off easily. This method, used to concentrate copper ore, is called froth flotation.
31. Name any four alloys of each of the metals: a) copper b) iron
a) Copper
AlloyComponentsUses
BrassCopper and zincUtensils, electrical appliances, machinery parts etc.
BronzeCopper and tinStatues, bells, coins and utensils.
German silverCopper, zinc and nickelUtensils, resistance coils, ornamental wares.
Gun metalCopper, tin and zincBarrels of guns, gears and castings.

b) Iron
AlloyComponentsUses
Stainless steelIron, carbon, nickel, chromiumSurgical instruments
Nickel steelIron and nickelUtensils drilling instruments
AlnicoIron, nickel, aluminium, cobaltMagnets
Invar steelIron, nickel, carbonMaking pendulum
NichromeIron, nickel, chromiumHeating coils.
SteelIron, carbonPipes, nails, sheets and cutting tools.



32. Show with an example that iron is capable of displacing less reactive metals from the solution of their salts.
Eg1: Iron displaces copper from copper sulphate solution and itself forms iron sulphate. This shows copper is less reactive than iron.
Fe + CuSO4 ®FeSO+ Cu¯
Eg2: Iron displaces silver from silver nitrate solution and itself forms ferrous nitrate. This proves that iron is more reactive than silver.
Fe + 2AgNo3 ® Fe (No3)2 + 2Ag¯
33. What is meant by froth flotation?
The method of concentration of copper ore by using water and oil is known as forth flotation.
34. Explain the method of purification of copper
Purification of copper is done by electrolytic refining. A set of thick impure copper plates are connected together and dipped in copper sulphate solution taken in a tank. Copper sulphate is the electrolyte. A set of thin pure copper plates are connected together and dipped into the same solution such that the pure copper plates are interposed between the impure copper plates
The set of pure copper plates is made cathode and the set of impure copper plates is made anode. This is done by connecting the sets to appropriate terminals of a battery. On passing direct current copper at the anode dissolves and get deposited on the cathode. The mass of cathode plates increases and that of anode plates decreases. Copper so obtained is 100% pure.
35. Write the Physical properties of copper and Iron.
Physical properties of copper: Copper is a rose red heavy metal. It is malleable and ductile. It is a very good conductor of electricity and heat. It is next only to silver in thermal conductivity. It has high melting point and high boiling point.
Physical properties: Iron is a greyish white solid metal. Pure iron is soft. Iron is a ferromagnetic substance. Its melting point is 1808K.
36. Explain the method of extraction of iron
Haematite is powdered and washed in a current of water to remove the unwanted earthly impurities. The earthly impurities such as sand, clay, organic wastes are called gangue. Even after removing some of the gangue materials, the ore would contain silicon dioxide as impurity.
To extract iron from haematite the following materials are needed. They are haematite (Fe2O3), lime stone (CaCO3) and coke (C).
The concentrated haematite, limestone and coke are mixed in the ratio 8:1:4. This mixture is called charge. The mixture is introduced into the blast furnace from the top of the furnace by the cup and cone arrangement. Hot air is blasted from bottom of the furnace. The following reactions take place and finally iron is produced.
1. Lime stone decomposes to calcium oxide
CaCO3----heat-à CaO + CO2.
Calcium oxide reacts with silica to forms calcium silicate
CaO + SiO2------> CaSiO3
2. Coke reacts with oxygen present in the air to form carbon dioxide
C + O2------> CO2.
3. Carbon dioxide reacts with more coke to produce carbon monoxide
CO2 + C ------> 2CO.
4. Carbon monoxide reduces the iron oxide to iron
Fe2O3 + 3CO ------> 2Fe + 3CO2.
Iron so produced will be in molten state and is collected at the bottom of the furnace.
Calcium silicate is a slag. It collects at the bottom of the furnace above the molten iron. The molten iron and the slag are removed from a separate outlet. Iron so obtained from the blast furnace is called cast iron or pig iron.