Question

Q1. Why does the colour of copper sulphate solution change when
an iron nail is dipped in it?
Q2. Give an example of a double displacement reaction other than
the one given in Activity 1.10.
Q3. Identify the substances that are oxidised and the substances
that are reduced in the following reactions.
(i) 4Na(s) + 0,(g) → 2Na,O(s)
(ü) CuO(s) + H,g) + Cu(s) + H2O(1)​

Answer 1

Answer:

1) When an iron nail immersed in the solution of copper sulphate than iron displaces copper from the solution of copper sulphate because iron is more reactive than copper. Therefore copper sulphate solution colour changes from blue to pale green.

2) Pb++ ions from lead nitrate combine with 2Cl ions from hydrochloric acid and a precipitate of lead chloride is formed. Thus, there is an exchange of ions between the two reactants i.e., lead nitrate and hydrochloric acid, and thus this reaction is a double displacement reaction.

3) The substance that added with oxygen is said to be oxidized whereas removal of oxygen is called as reduction and the substance is said to be reduced.

(i) Na changes to Na2O. Hence, oxygen added so here Na oxidized and O2 reduced.

(ii) CuO changes to Cu hence oxygen is removed from CuO. Hence, CuO is reduced and H2 is oxidized.