Question

Which of the following does not produce H${}_2$ at the anode on electrolysing using Pt electrode?

• A. molten CaH${}_2$
• B. $NaCl\left(aq\right)$
• C. CuSO${}_4$ (aq)
• D. dil H${}_2$SO${}_4$

Answer 1

Answer: (B), (C), (D)

The correct options are
B CuSO${}_4$ (aq)
C dil H${}_2$SO${}_4$
D $NaCl\left(aq\right)$

The electrolysis of molten calcium hydride using platinum electrodes produces hydrogen at anode because the standard reduction potential for the reduction of water is higher than that for the reduction of $C{a}^{2+}$.
Similarly the electrolysis of aqueous NaCl, will produce hydrogen at the anode. This is because, the discharge potential of hydrogen ions is lower than that of sodium ions.
The electrolysis of dil sulfuric acid with platinum electrodes will produce hydrogen at the anode.
The electrolysis of aqueous copper sulphate with platinum electrodes will not produce hydrogen at the cathode as the discharge potential of hydrogen ions is higher than the discharge potential of cupric ions.