Question

When nickel is placed in dilute acid, H2(g) is spontaneously evolved. When silver is placed in dilute acid, no gas is evolved. Using data from appendix 11, explain in detail why this is the case.

Answer 1

When Nickel is placed in water, reaction is:

Ni + 2H₂O   Ni(OH)₂ +H₂

and When Silver is placed in water, reaction is:

2Ag + 2H₂O 2AgOH + H₂

Reduction potential value of Ni = -0.25 V

Reduction potential value of Ag = 0.80 V

Reduction potential Value of H₂ = 0.00 V

if a element has Higher reduction potential value then other, then it will reduces and other with lower reduction potential value, will oxidise as it has less tendency to gain electrons in comparison to other. SO, one with lower reduction potential will loose electrons and other will gain

Thus, w.r.t H₂ , Nickel has negative reduction potential or lower reduction potential value

Thus, Ni will oxidise and loose electrons and H will gain these electrons.

Similarly, Ag has higher reduction potential value then H₂. So, Ag has more potential to reduce. But Ag is already in reduced state and Hydrogen is already in oxidized state(H⁺ in water).

Hence, no reaction takes place.