metallurgy

Question 1

1. Element X is a metal with a valency 2. Element Y is a non-metal with a valency 3.
   (i) Writ equations to show how X and Y form ions.
   (ii) If Y is a diatomic gas, write the equations for the direct combination of X and Y to form a compound.

Answer 1

(i) X – 2e^- → X⁺⁺

Y + 3e^- → Y^—

(ii) 3X⁺² + 2Y^-3 → X³Y².

Question 2

(i) Complete the missing statements:
Metals are _________ while non-metals are poor conductor of heat. Metals are malleable while non-metals are _______ . Metals form positive ions while non-metals form ______. Non-metals form acidic oxides while metals form _________ .

Answer 2

Good conductor of heat; Brittle; Negative ions; Basic oxide.

Question 3

Name: (a) The metal which is liquid at room temperature. (b) The allotrope of the non-metal carbon which conducts electricity. How many valence electrons are present in (c) metals (d) non-metals.

Answer 3

(a) Mercury (b) Graphite (c) 1 to 3 (d) 4 to 8.

Question 4

What metallic property is shown by the non-metal graphite.

Answer 4

Conduction of electricity.

Question 5

X is an element in the form of a powder. X burns in oxygen and the product is soluble in water. The solution is tested with litmus. Write down only the word which will correctly complete each of the following:

(a) If X is a metal, then the litmus will turn _______. If X is non-metal, then the litmus will turn ______.
(b) If X is a reactive metal, then _______ will be evolved when X reacts with dilute sulphuric acid.
(c) If X is a metal it will form _______ oxide, which will form ________ solution with water.
(d) If X is a non-metal it will not conduct electricity unless it is carbon in the form of _______.

Answer 5

)(a) Blue; Red. (b) Hydrogen. (c) Basic; alkaline.(d) Graphite.

Question 6

Compare the properties of a typical metal and a non-metal on the basis of the following:

(a) Electronic configuration
(b) Oxidizing or reducing action
(c) Nature of the oxides
(d) Conductivity of heat and electricity.

Answer 6

Question 7

Name:

(a) A non-metal that has a metallic lustre and sublimes on heating.
(b) An allotrope of a non-metal that allows electricity to pass through it.

Answer 7

(a) Iodine
(b) Graphite.

Question 8

. (i) Cations are formed by ___________ (loss / gain) of electrons and anions are formed by (loss / gain) of electrons.[Choose the correct words to fill in the blanks.]

Answer 8

) loss; gain.

Question 9

State the term used for: - An oxide, which forms salts when it reacts with both acids and alkalis.

Answer 9

Amphoteric oxide.

Question 10

When a metal atom becomes an ion:

(a) it loses electrons and is oxidized
(b) it gains electrons and is reduced
(c) it gains electrons and is oxidized (d) it loses electrons and is reduced.

[Choose the correct answer from the choices (a), (b), (c) and (d)]

Answer 10

(a).

Question 11

With reference to the reduction of copper oxide, iron (II) oxide, lead (II) oxide and magnesium oxide by hydrogen, place the oxides in order of increasing case of reduction.

Answer 11

The order of oxides in order of increasing order of reduction is:

MgO < FeO < PbO < CuO.

Question 12

Write balanced equations for the following reactions: (a) Reduction of copper oxide by hydrogen. (b) Reduction of iron (III) oxide by carbon monoxide. (c) Reduction of lead (II) oxide by carbon.

Answer 12

(a) CuO + H2 → Cu + H2O.
(b) Fe2O3 + 3CO → 2Fe + 3CO2.
(c) PbO + C → Pb + CO.

Question 13

A strip of copper is placed in four different colourless salt solutions. They are KNO3, AgNO3, Zn(NO3)2, Ca(NO3)2. Which one of the solutions will finally turn blue.

Answer 13

AgNO3 solution will finally turn blue.

Cu + 2AgNO3 → Cu(NO3)2 + 2Ag.

Question 14

Select the correct compound from the list – Ammonia, Copper oxide, Copper sulphate, Hydrogen chloride, Hydrogen sulphide, Lead carbonate – which matches with the description given below:

(a) This compound can be reduced to copper when heated with coke.
(b) A white solid which gives a yellow residue on heating.

Answer 14

(a) Copper oxide (b) Lead carbonate.

Question 15

(i) Name: (a) a carbonate not decomposed by heat. (b) a green carbonate which turns black on heating.

Answer 15

(a) Potassium and sodium carbonates. (b) CuCO3.

Question 16

From the metals copper, iron, magnesium, sodium and zinc, select a different metal in each case which :

(a) Does not react with dilute hydrochloric acid.
(b) can form 2+ and 3+ ions.
(c) has a hydroxide that reacts with both acids and alkalis.
(d) does not react with cold water but reacts with steam when heated.
(e) Arrange the metals in decreasing order of reactivity.

Answer 16

(a) Copper (b) Iron (c) Zinc (d) Iron, Magnesium, Zinc
(e) Sodium, Magnesium, Zinc, Iron, Copper.

Question 17

(i) Name the process of heating an ore to a high temperature in the presence of air.

Answer 17

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Roasting

Question 18

By what chemical process is the amount of carbon in cast iron decreased to make steel.

Answer 18

Oxidation.

Question 19

Question .7. (i) For each substance listed below, explain its significance in the extraction of aluminium: (a) Bauxite (b) Sodium hydroxide (c) Cryolite (d) Graphite.

Answer 19

(a) Bauxite is the most common ore of Aluminium.
(b) Sodium hydroxide is used for the purification of Bauxite by Baeyer’s process.
(c) Cryolite is added to pure alumina to decrease the melting point or fusion temperature of pure Alumina.
(d) Graphite acts as anode.

Question 20

Relating to the extraction of aluminium by electrolysis: (a) Give the equation for the reaction which takes place at the cathode. (b) Explain why it is necessary to renew the anode periodically.

Answer 20

(a) Al3+ + 3e- → Al.
(b) Anode is renewed periodically as they get oxidized.

Question 21

In order to obtain aluminium, the following inputs are required: Bauxite, sodium hydroxide and graphite. The aluminium compound in bauxite is aluminium oxide and the main impurity is iron (III) oxide. Aluminium is obtained by the electrilysis of aluminium oxide dissolved in cryolite. (1) When bauxite is treated with sodium hydroxide solution what happens to the (a) aluminium oxide (b) iron (III) oxide. (2) Name the process used for the purification of bauxite. (3) Write the equation for the action of heat on aluminium hydroxide.

Answer 21

(1) (a) It is dissolved in sodium hydroxide to form sodium aluminate.(b) iron oxide is not soluble in sodium hydroxide and is removed.
(2) Baeyer’s process.
(3) 2Al(OH)3 → Al2O3 + 3H2O.

Question 22

Write the formula of cryolite

Answer 22

Na₃AlF₆.

Question 23

Aluminium is extracted from its chief ore, bauxite.

(a) Write three balanced equations for the purification of bauxite by Hall’s process.
(b) Name the chemical used for dissolving Al2O3. In which state of subdivision is the chemical used.
(c) Write an equation for the reaction which takes place at the anode during the extraction of aluminium by the electrolytic process.
(d) Mention one reason for the use of aluminium in thermite welding.

Answer 23

(a) Na3AlF6 ↔ 3Na+ + Al+++ + 6F-

CaF2↔ Ca++ + 2F-

Al2O3 ↔ 2Al+++ + 3O–

(b) Fluorspar and cryolite. Alumina – 20%, Cryolite – 60%, Fluorspar – 20%.
(c) 2O– – 4e- → O2.
(d) Aluminium has a high affinity for oxygen. It readily removes oxygen from oxides of less reactive metals.

Fe2O3 + 2Al → Al2O3 + 2Fe + Δ.

Question 24

A to F below relate to the source and extraction of either Zinc or Aluminium.

A: Bauxite, B: Coke, C: Cryolite, D: Froth floatation, E: Sodium hydroxide solution, F: Zinc blend.

(a) Write down the three letters each from the above list which are relevant to – (1) Zinc (2) Aluminium.
(b) Fill in the blanks using the most appropriate words from A to F : -
(1) The ore from which aluminium is extracted must first be treated with _______ so that pure Aluminium oxide can be obtained.
(2) Pure Aluminium oxide is dissolved in ________ to make a conducting solution.
(c) Write the formula of Cryolite.

Answer 24

(a) (1) B, D, F. (2) A, C, E.
(b) (1) Sodium hydroxide solution. (2) Cryolite.
(c) Na3AlF6.

Question 25

Name the compound added to lower the fusion temperature of the electrolytic bath in the extraction of Al.

Answer 25

Cryolite.

Question 26

Write down the word which correctly completes the following sentence: - “By dissolving aluminium oxide in cryolite a _________ [conducting / non-conducting] solution is produced”.

Answer 26

Conducting.

Question 27

Why is so much graphite required for this electrolytic process. Write the equation for the reaction which take place at the cathode.

Answer 27

Graphite reacts with oxygen produced to form oxides of carbon and gets consumed.

2C + O2 → 2CO

2CO + O2 → 2CO2.

At cathode : 2Al3+ + 6e- → 2Al.

Question 28

(i) Write the equations for the reaction of zinc with each of the following: - (a)Sodium hydroxide solution.
(b) Dilute sulphuric acid.
(c) Copper sulphate solution.

Answer 28

(a) Zn + 2NaOH → Na2ZnO2 + H2.
(b) Zn + H2SO4 → ZnSO4 + H2.
(c) Zn + CuSO4 → ZnSO4 + Cu.

Question 29

) Write the balanced equations for the preparation of the following compounds (as the major product) starting from iron and using only one other substance:

(a) iron (II) chloride
(b) iron (III) chloride
(c) iron (II) sulphate
(d) iron (II) sulphid

Answer 29

(a) Fe + 2HCl → FeCl2 + H2.

                       Δ  (b) 2Fe + 3Cl2 → 2FeCl3.

(c) Fe + H2SO4 (dil) → FeSO4 + H2.

               Δ  (d) Fe + S → FeS + Δ .

Question 30

Write balanced equation for – Al powder when warmed with hot and concentrated caustic soda solution.

Answer 30

2Al + 2NaOH + 2H2O → 2NaAlO2 + 3H2.

Question 31

(iv) To protect iron from rusting it is coated with a thin layer of zinc. Name the process.

Answer 31

Galvanising.

Question 32

Which particular property of cast iron makes it unsuitable for the construction of bridges.

Answer 32

Brittleness.

Question 33

i) What is an alloy?

Answer 33

An alloy is a homogeneous mixture of two or more metals or non-metals mixed in a molten state.

Question 34

An alloy usually has some property which makes it particularly useful. What is the special property of: (a) Duralumin (b) Type metal.

Answer 34

(a) Light and strong or high tensile strength. (b) Expands on cooling.

Question 35

` Which metal is added to steel to make stainless steel.

Answer 35

Chromium and Nickel.

Question 36

Are liquid zinc and liquid lead miscible or immiscible? Name the alloy formed between Zn and Cu.

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Answer 36

Immiscible. Brass.

Question 37

In construction work, state why the alloy duralumin is use rather than pure aluminium.

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Answer 37

) In construction work, duralumin is used rather than pure aluminium due to following reasons:

(a) Aluminium is light and not strong but duralumin is light and strong.
(b) Aluminium is attacked by moist air whereas duralumin is unaffected by moist air.
(c) Aluminium undergo corrosion whereas duralumin is corrosion resistant.
(d) Aluminium has low tensile strength whereas duralumin has high tensile strength.

Question 38

Calcium, Copper, Lead, Aluminium, Zinc, Chromium, Magnesium, Iron. Choose the major metals from the list given above to make the following alloys: (a) Stainless steel (b) Brass.

Answer 38

) (a) Iron and Chromium. (b) Copper and Zinc.

Question 39

List 1 contains metals / alloys 1, 2, 3, 4, 5 and list 2 contains their uses A, B, C, D, E.

Answer 39

Metal / Alloy

1 - B

2 - D

3 - E

4 - A

5 - C