Question

Which of the following metal do not evolve $H_2$ gas from dil. acid?

• A. $A\left(E{}_{A^{+}/A}^{\circ }=0.25V\right)$
• B. $B\left(E{}_{B/B^{+}}^{\circ }=0.22V\right)$
• C. $C\left(E{}_{C^{+}/C}^{\circ }=0.30V\right)$
• D. $D\left(E{}_{D/D^{+}}^{\circ }=0.44V\right)$

Answer 1

Answer: (A), (C)

The correct options are
A $A\left(E{}_{A^{+}/A}^{\circ }=0.25V\right)$
C $C\left(E{}_{C^{+}/C}^{\circ }=0.30V\right)$

Comparing the reduction potential with $H^{+}/H_2$ cell. The one having higher reduction potential will not allow $H^{+}$ to be reduced.

$\therefore A(E_{A^{+}/A}^o=0.25$ $V)$ and $C(E_{C^{+}/C}^o=0.30$ $V)$ will not allow $H_2$ gas to evolve.

$2A^{+}+H_2⟶2A+2H^{+}$

$2C^{+}+H_2⟶2C+2H^{+}$