Redox Equilibrium

Free sample questions

Redox Equilibrium — sample Chemistry questions with answers

1. Question 1

   In the reaction $\text{Zn}+{\text{Cu}}^{2+}\to {\text{Zn}}^{2+}+\text{Cu}$, what process does zinc undergo?

   • AOxidation
   • BReduction
   • CNeutralization
   • DPrecipitation

   Answer: A. Oxidation

   Zinc loses electrons and its oxidation number increases from $0$ to $+2$, so it undergoes oxidation.

2. Question 2

   What is the oxidation number of manganese in ${\text{KMnO}}_4$?

   • A$+2$
   • B$+4$
   • C$+6$
   • D$+7$

   Answer: D. $+7$

   Potassium $+1$, oxygen $-2$ (4 atoms), total charge $0$, so $+1+x+4(-2)=0$, $x=+7$.

3. Question 3

   In an electrolytic cell, ${\text{Na}}^{+}$ and ${\text{Cl}}^{-}$ ions are present in molten $\text{NaCl}$. At the anode, which species is discharged?

   • A${\text{Na}}^{+}$
   • B${\text{Cl}}^{-}$
   • C${\text{H}}_2\text{O}$
   • D${\text{OH}}^{-}$

   Answer: B. $\text{Cl}^-$

   At the anode, anions are discharged. ${\text{Cl}}^{-}$ is more easily discharged than ${\text{OH}}^{-}$ in molten (no water).

4. Question 4

   Which of the following is NOT a reducing agent?

   • A$\text{Na}$
   • B${\text{H}}_2$
   • C${\text{Fe}}^{2+}$
   • D${\text{Cl}}_2$

   Answer: D. $\text{Cl}_2$

   Chlorine (${\text{Cl}}_2$) tends to accept electrons (oxidises itself), so it is an oxidizing agent, not a reducing agent.

5. Question 5

   What is the product at the cathode when ${\text{CuSO}}_4$ solution is electrolysed using copper electrodes?

   • AOxygen gas
   • BCopper
   • CHydrogen gas
   • DChlorine gas

   Answer: B. Copper

   ${\text{Cu}}^{2+}$ ions are discharged at the cathode to form copper metal.