NCERT Class X Science Class: Chapter –3. Metals and Nonmetals– Part-7

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Short Answer Questions

Question 37:

Iqbal treated a lustrous, divalent element M with sodium hydroxide. He observed the formation of bubbles in reaction mixture. He made the same observations when this element was treated with hydrochloric acid. Suggest how he can identify the produced gas. Write chemical equations for both the reactions.


The element is a metal

The produced gas can be identified by bringing a burning match stick near the reaction vessel, a pop sound is produced

Question 38:

During extraction of metals, electrolytic refining is used to obtain pure metals.

  1. Which material will be used as anode and cathode for refining of silver metal by this process?

  2. Suggest a suitable electrolyte also.

  3. In this electrolytic cell, where do we get pure silver after passing electric current?


  1. Anode: Impure silver

Cathode: Pure silver

  1. Electrolyte: Silver salt, such as

  2. We get pure silver at cathode

Question 39:

Why should the metal sulphide and carbonates be converted to metal oxides in the process of extraction of metal from them?


It is easier to obtain metal from its oxide, as compared from its sulphide and carbonates.

Sulphide ores and carbonates are thermodynamically more stable than and hence cannot converted by using coke as reducing agent . Hence it is better to convert sulphide ore to oxide form and then apply smelting.

Question 40:

Generally, when metals are treated with mineral acids, hydrogen gas is liberated but when metals (except), treated with, hydrogen is not liberated, why?


It is because is a strong oxidizing agent. It oxidises the produced to

is a very strong oxidizing agent, (it has a very strong liking for Hydrogen and doesn't want it to stay alone). As soon as Hydrogen is formed, helps in oxidizing it into water.

Question 41:

Compound X and aluminium are used to join railway tracks.

  1. Identify the compound X

  2. Name the reaction

  3. Write down its reaction.


  1. The compound is Iron (III) oxide.

  1. The reaction is a thermite reaction.

The thermite reaction is the reaction between the iron (III) oxide and aluminium. This reaction produces a lot of heat that melts the iron to form molten iron that is used as the fuse to join the rails.

  1. The balanced reaction is as follows:

Question 42:

When a metal X is treated with cold water, it gives a basic salt Y with molecular formula and liberates a gas Z which easily catches fire. Identify X, Y and Z and also write the reaction involved.


Sodium (Na) and potassium (K) react with cold water to form basic salt respectively. The molecular mass of is .

Therefore, . The gas liberated during the reaction is hydrogen Therefore

Heat energy

Question 43:

A non-metal X exists in two different forms Y and Z. Y is the hardest natural substance, whereas Z is a good conductor of electricity. Identify X, Y and Z.


Y, that is, the hardest naturally occurring substance in the world is diamond.

The substance Z, which is a good conductor of electricity is Graphite.

Both diamond and Graphite come from Carbon, a non-metal which lacks luster, and also does not conduct electricity.

Carbon, diamond, and graphite have different properties due to the crystal structures of each.

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