Metallurgy Short Ans Concise Class-10 ICSE Chemistry Selina Solutions Chapter-7. We Provide Step by Step Answer of Short Ans Questions of Miscellaneous Exercise-7 for ICSE Class-10. The given Solutions is according to the Latest editions. Visit official Website CISCE for detail information about ICSE Board Class-10.
Metallurgy Short Ans Concise Class-10 ICSE Chemistry Selina Solutions Chapter-7
| Board | ICSE |
| Book / Publication | Concise / Selina |
| Subject | Chemistry |
| Class | 10th |
| Writer | Dr SP Singh |
| Chapter-7 | Metallurgy |
| Topics | Short Ans (Miscellaneous Exercise) |
| Edition | 2025-2026 |
Short Ans Questions on Metallurgy
Page-142
Que-1: State the main components of the following alloys:
(i) Brass
(ii) Duralumin
(iii) Bronze
Ans:
(i) Brass: Main components of brass are copper and zinc.
(ii) Duralumin: Main components of duralumin are aluminium, magnesium, copper and manganese.
(iii). Bronze: Main components of bronze are copper, zinc and tin.
Que-2: For each of the substance listed below, describe the role played in the extraction of aluminium.
(i) Cryolite
(ii) Sodium hydroxide
(iii) Graphite
Ans: In the extraction of aluminium, the given compounds play the following roles:
(i) Cryolite: It lowers the fusion temperature from 2050°C to 950°C and enhances conductivity.
(ii) Sodium hydroxide: Two roles are play with sodium hydroxide in the extraction of aluminium.
First, finely grinded bauxite (ore of aluminium) should heat under pressure with conc. caustic soda solution (NaOH solution) for 2-8 hours at 140°C to 150°C to produce sodium aluminate. The chemical equation is as follows:
Al2O3.2H2O + 2NaOH → 2NaAlO2 + 3H2O
Second, on diluting sodium aluminate with water and cooling to 50°C, sodium aluminate is hydrolysed to give aluminium hydroxide as precipitate. Here, the impurities dissolve in sodium hydroxide.
(iii) Graphite: Thick rods of graphite are suspended in the fused electrolyte. They act as an anode where oxygen gas is discharged.
Que-3: Write the chemical formula of one main ore of iron and aluminium.
Ans: Ores of iron
| Name | Chemical name | Formula |
| Red Haematite | Anhydrous ferric oxide | Fe2O3 |
| Brown Haematite | Hydrated ferric oxide | 2Fe2O3.3H2O |
Ores of aluminum
| Name | Chemical name | Formula |
| Bauxite | Hydrated aluminium oxide | Al3O32H2O |
| Cryolite | Sodium aluminium oxide | Na3AlF6 |
Que-4: State the property of the metal being utilised in the following:
| Use of metal | Property |
| Zinc in galvanisation | |
| Aluminium in thermite welding |
Ans:
| Use of metal | Property |
| Zinc in galvanisation | Zinc oxidises more readily than iron, thus preventing the rusting of iron. |
| Aluminium in thermite welding | Aluminium is a good reducing agent. |
Que-5: The following questions are relevant to the extraction of aluminium:
(i) State the reason for addition of caustic alkali to bauxite ore during purification of bauxite.
(ii) Give a balanced chemical equation for the above reaction.
(iii) Along with cryolite and alumina, another substance is added to the electrolyte mixture. Name the substance and give one reason for the addition.
Ans:
(i) Caustic alkali is added to bauxite ore during extraction as the insoluble part of bauxite is removed and the alumina component is then precipitated.
(ii) The reaction is as follows:
Al2O3.2H2O + 2NaOH →2NaAlO2 + 3H2O
(iii) Fluorspar is added along with cryolite and alumina because this helps the mixture to fuse at instead of, and the aluminium obtained at this temperature is in the liquid state.
Que-6: Write the constituents of the electrolyte for the extraction of aluminium.
Ans: Constituents of the electrolyte for the extraction of aluminium are pure alumina (, cryolite (Na3AlF6) and fluorspar .
Que-7: Write the equation for the reaction where the aluminium oxide for the electrolytic extraction of aluminium is obtain on heating aluminium hydroxide.
Ans: Conversion of Al(OH)3 – to pure alumina – heat on Al(OH)3
Que-8: Write the equation for the reaction that occurs at the cathode during the extraction of aluminium by electrolysis.
Ans: Reaction at cathode:
Al3+ + 3e– ⟶ Al
Que-9: Explain why it is preferable to use a number of graphite electrodes as anode instead of a single electrode, during the above electrolysis.
Ans: Anode should replace from time to time as it gets oxidise with oxygen evolve at the anode.
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