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

NCERT Solution: Metals and Non-metals

Generally, when metals are treated with mineral acids, hydrogen gas is liberated but when metals (except Mn and Mg), treated with HNO3, hydrogen is not liberated, why?

Nitric acid is a potent oxidizing agent. It reacts with hydrogen to form water. Due to this, when a metal is treated with nitric acid, hydrogen gas is not liberated.

Compound X and aluminium are used to join railway tracks. (a) Identify the compound X (b) Name the reaction (c) Write down its reaction.

Compound X is iron oxide Fe₂O₃ . This reaction is called thermite reaction. This reaction is given by following equation:

2 Al + Fe₂O₃ → 2Fe +Al₂O₃ + heat

When a metal X is treated with cold water, it gives a basic salt Y with molecular formula XOH (Molecular mass = 40) and liberates a gas Z which easily catches fire. Identify X, Y and Z and also write the reaction involved.

X is sodium because molar mass of NaOH is 40; which can be shown as follows:

Na (23) + O(16) + H (1) = 40

So, Y is NaOH

Z is hydrogen gas which easily catches fire.

Reaction between sodium and water can be given as follows:

2Na + 2H₂O → 2 NaOH + H₂

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

X is carbon. Diamond and graphite are allotropes of carbon. Diamond is the hardest natural substance and hence Y is diamond. Graphite is a good conductor of electricity and hence Z is graphite.

The following reaction takes place when aluminium powder is heated with MnO₂

3MnO₂(s) + 4Al(s) → 3Mn(l) +2Al₂O₃ + Heat

(a) Is aluminium getting reduced?

(b) Is MnO₂ getting oxidised?

Ans. In this reaction, aluminium is getting oxidized because oxygen gets combined to it. Since oxygen is removed from manganese dioxide hence MnO₂ is getting reduced.

What are the constituents of solder alloy? Which property of solder makes it suitable for welding electrical wires?

Lead and tin are the constituents of solder alloy. Solder alloy has a low melting point; which makes it suitable for welding electrical wires.

A metal A, which is used in thermite process, when heated with oxygen gives an oxide B, which is amphoteric in nature. Identify A and B. Write down the reactions of oxide B with HCl and NaOH

Metal A is aluminium and B is Al₂O₃ .

Reaction of aluminium oxide with HCl:

Al₂O₃ + HCl → 2AlCl₃ + 3H₂O

Reaction of aluminium oxide with NaOH:

Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O

A metal that exists as a liquid at room temperature is obtained by heating its sulphide in the presence of air. Identify the metal and its ore and give the reaction involved.

This metal is mercury because mercury exists as liquid at room temperature. Mercury ore is called cinnabar (HgS). When cinnabar is heated in presence of air, following reaction takes place:

2HgS + O₂ → 2 HgO + 2 SO₂

Mercury oxide is further heated to obtain mercury:

2HgO → 2Hg + O₂