Question

The standard potentials at 25⁰C for the following half

reactions are given as

$Zn^{2 +} + 2e^{-}\overset{\quad\quad}{\rightarrow}Zn,E^{O} = - 0.762VMg^{2 +} + 2e^{-}\overset{\quad\quad}{\rightarrow}Mg,E^{O} = - 2.37V$When zinc dust is added to a solution of magnesium chloride

• A. No reaction will take place
• B. Zinc Chloride is formed
• C. Zinc dissolve in solution
• D. Magnesium is precipitated

Answer 1

Answer: (A)

No reaction will take place

Answer 2

$Zn + MgCI_{2}\overset{\quad\quad}{\rightarrow}ZnCI_{2} + Mg$

$\therefore{E^{0}}_{cell} = {E^{0}}_{zn/zn^{+ 2}} + {E^{0}}_{Mg^{+ 2}/Mg} = + 0.762 - 2.37 = - 1.608V$Here, ${E^{0}}_{cell}$is negative so no reaction will take place