Question

In which of the following reactions conc. H2SO4 is used as an oxidising reagent?
(i) CaF2 + H2SO4 ⎯→ CaSO4 + 2HF
(ii) 2HI + H2SO4 ⎯→ I2 + SO2 + 2H2O
(iii) Cu + 2H2SO4 ⎯→ CuSO4 + SO2 + 2H2O
(iv) NaCl + H2SO4 ⎯→ NaHSO4 + HCl


NCERT Class XII
Chemistry - Exemplar Problems

Chapter 7. The p-block elements

Answer 1

Concept: An oxidising agent, often known as an oxidizer or an oxidant, is a type of chemical that has the tendency to oxidise other substances, increasing their oxidation state by causing them to lose electrons. Halogens (such as chlorine and fluorine), oxygen, and hydrogen peroxide are typical examples of oxidising agents ($H_2O_2$).

Given: conc. $H_2SO_4$ is used as an oxidising reagent

To find: the reactions in which conc. $H_2SO_4$ is used as an oxidising reagent

Solution:

In the given 4 reactions, (ii) and (iii) represent oxidising behaviour of $H_2SO_4$. As we know that oxidising agent reduces itself as oxidation state of central atom decreases. Here,

   -1          -6                         0      -4

$2HI + H_2SO_4 ----- > I_2 + SO_2 + 2H_2O$

0             +6                         +2           +4

$Cu +2H_2SO_4 ----- > CuSO_4 + SO_2 +2H_2O$

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