Chemistry 9701 · AS & A Level · Electrochemistry

Electrochemistry — practice question

(a)[2]

Define what is meant by standard cell potential.

(b(i))[4]

Draw a fully labelled diagram of the experimental arrangement you would use to measure the standard electrode potential of the $\text{Pb}^{2+}$(aq)/Pb(s) electrode. Include the required chemicals.

(b(ii))[2]

The $E^\circ$ for a $\text{Pb}^{2+}$(aq)/Pb(s) electrode is $-0.13\,\text{V}$. Suggest how the $E$ for this electrode would change relative to its $E^\circ$ value if the concentration of $\text{Pb}^{2+}$(aq) ions is lowered. Show your choice by putting a tick (✓) in the correct box in the table. Explain your answer.

(c(i))[2]

Calculate the mass of Pb converted to $\text{PbSO}_4$ when a current of $0.40\,\text{A}$ is supplied by the cell for $80\,\text{minutes}$.

(c(ii))[1]

Complete the half-equation for the reaction happening at the positive electrode. $\text{PbO}_2$(s) + \text{SO}_4^{2-}$(aq) + \ldots + \ldots \rightarrow \text{PbSO}_4$(s) + \ldots$

(d)[2]

The diagrams show how the voltage across two different cells changes with time while each cell is used to supply an electric current. Suggest a reason why the voltage of the lead-acid cell changes after several hours, and why the voltage of the fuel cell stays constant.

Worked solution & mark scheme

This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: Difference in potential between two half-cells

  • Full mark scheme, point by point
  • Step-by-step worked solution
  • Write your answer & get it marked instantly by AI