Question

Which of the following are redox reactions? 1. LiH + HCl → LiCl + H2 2. Na2S + CuCl2 → CuS + 2 NaCl 3. 3 Cu + 8 H+ + 2 NO3- → 3 Cu2+ + 2 NO + 4 H2O 4. Ba(OH)2 + 2 HNO3 → Ba(NO3)2 + 2 H2O 5. ZnCl2 + 2 KOH → 2 KCl + Zn(OH)2

Answer 1

1. LiH + HCl → LiCl + H2

Oxidation state of H changes from +1 in HCl to 0 H2

Oxidation state of H changes from -1 in LiH to 0 in H2

So, there is oxidation as well as reduction taking place.

This is redox reaction.

2. Na2S + CuCl2 → CuS + 2 NaCl

Oxidation state of Na is +1 on both sides

Oxidation state of Cu is +2 on both sides

Oxidation state of S is -2 on both sides

Oxidation state of Cl is -1 on both sides

None of the oxidation state is changing.

So, this is redox reaction

3. 3 Cu + 8 H+ + 2 NO3- → 3 Cu2+ + 2 NO + 4 H2O

Oxidation state of Cu changes from 0 to +2

Oxidation state of N changes from +5 to +2

So, there is oxidation as well as reduction taking place.

This is redox reaction.

4. Ba(OH)2 + 2 HNO3 → Ba(NO3)2 + 2 H2O

None of the oxidation state is changing.

So, this is redox reaction

5. ZnCl2 + 2 KOH → 2 KCl + Zn(OH)2

None of the oxidation state is changing.

So, this is redox reaction

Answer: 1 and 3