Metals and Non-metals NCERT Solution, study material, CBSE Notes

NCERT Solution: Metals and Non-metals

Give the formulae of the stable binary compounds that would be formed by the combination of following pairs of elements.

(a) Mg and N₂
Ans. Magnesium nitride (Mg₃N₂)
(b) Li and O₂
Ans. Lithium oxide (Li₂O)
(c) Al and Cl₂
Ans. Aluminum chloride (AlCl₃)
(d) K and O₂
Ans. Potassium oxide (K₂O)

What happens when

(a) ZnCO₃ is heated in the absence of oxygen?
Ans. When zinc carbonate is heated in the absence of oxygen, we get zinc oxide and carbon dioxide.

ZnCO₃ → ZnO + CO₂

(b) a mixture of Cu₂O and Cu₂S is heated?
Ans. When a mixture of copper oxide and copper sulphide is heated, we get pure copper.
2Cu₂O + Cu₂S → 6Cu + SO₂

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

(a) Identify A, B and C

Ans. A is carbon, B is carbon monoxide and C is carbon dioxide.

(b) To which Group of Periodic Table does A belong?

Ans. Carbon belongs to group 14.

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

Iron and copper are good conductors of heat and electricity. Lead and mercury are poor conductors of heat and electricity.

Name one metal and one non-metal that exist in liquid state at room temperature. Also, name two metals having melting point less than 310 K (37°C)

Mercury (metal) and bromine (non-metal) exist in liquid state at room temperature. Caesium and gallium are metals with melting point less than 310 k.

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.

A is calcium. It reacts with water to give calcium hydroxide. B is calcium hydroxide and is used for white washing. C is calcium oxide. The reactions are as follows:

Ca + 2H₂O → Ca(OH)₂ + H₂
Ca(OH)₂ → CaO + H₂O
CaO + H₂O → Ca(OH)₂

An alkali metal A gives a compound B (molecular mass = 40) 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.

A is sodium because molar mass of NaOH is 40; which can be shown as follows:
Na (23) +O (16) +H(1)=40
So, B is NaOH
When sodium hydroxide is treated with aluminium oxide, we get sodium aluminate. So, C is sodium aluminate. Following reaction happens in this case:
Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O