NCERT Class X Science Class: Chapter – 3. Metals and Nonmetals – Part-9 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 50:

A non-metal A is an important constituent of our food and forms two oxides B and C. Oxide B is toxic whereas C causes global warming

  1. Identify A, B and C
  2. To which Group of Periodic table does A belong?


  1. A is carbon, B is carbon monoxide and C is carbon dioxide
  2. A belongs to Group – 14 of the Periodic table

Question 51:

Give two examples each of the metals that are good conductors and poor conductors of heat respectively.


  1. Good conductor: Silver (Ag) and Copper (Cu) .
Image the Good Conductors
  1. Poor conductor: Mercury (Hg) and Lead (Pb) :
Images Show in Poor Conductor

Question 52:

Name one metal and one non-metal that exist in liquid state at room temperature. Also name two metals having melting point less than


Following are the metals and non-metals, which exist in liquid state at room temperature.

Metal – Mercury (Hg)

Non-metal – Bromine (Br)

Images Show in Metal and Non-Metal

Two metals with melting points less than are Cesium and Gallium

Images Show in Two Metals with Melting Points

Question 53:

An element A reacts with water to form a compound B which is used in white washing. The compound B on heating forms an oxide C which on treatment with water gives back B. Identify A, B and C and give the reactions involved.


Element A is calcium (Ca) . When it reacts with water, it forms calcium hydroxide. Thus, compound B is calcium hydroxide , which is used in white washing.


Compound B on heating gives

Thus, C is calcium oxide

on treatment with water gives back .

Question 54:

An alkali metal A gives a compound B on reacting with water. The compound B gives a soluble compound C on treatment with aluminium oxide. Identify A, B and C and give the reaction involved.


For A:

Alkali metals are sodium, potassium, lithium etc.

On reacting with water, they give metal hydroxide.

Hydroxide molecular mass

As molecular mass of the metal hydroxide is 40, n = 1 or 2, and correspondingly the molecular mass of metal is 23 or 6.

That is metal A is either sodium or lithium

For B:

Sodium hydroxide or lithium hydroxide. Lithium hydroxide - molecular mass is not 40

Therefore metal A is Sodium: Na and compound B is sodium hydroxide.


Therefore, compound B is sodium hydroxide

For C:

Sodium hydroxide reacts with aluminium oxide to give sodium aluminate Thus, C is sodium aluminate . The reaction involved is

Question 55:

Give the reaction involved during extraction of zinc from its ore by

  1. Roasting of zinc ore
  2. Calcination of zinc ore


Extraction of zinc is shown in below figure:

Images Show in Extraction of Zinc

For (A) :

The roasting is the process of burning of a ore in the presence of the excess air.

Therefore, the zinc sulphide will be heated with excess of the air.

The following reaction will be performed

For (B) :

Whereas, the calcination is the process of heating of a ore in the absence of the oxygen,

Therefore, this will perform the following reaction.

Question 56:

A metal M does not liberate hydrogen from acids but reacts with oxygen to give a black colour product. Identify M and black coloured product and also explain the reaction of M with oxygen.


Metal m is copper which does not liberate when it reacts with acid as copper is least reactive than Hydrogen. Therefore, it cannot displace hydrogen from .

Copper reacts with oxygen to form copper (II) oxide, which is black in colour

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