Chemistry - Redox Reactions Question with Solution | TestHub

Moles of electrons = (6.02 × $10^{22})/(6.022$ × $10^{23}$) ≈ 0.1 mol. ${\mathrm{M}}^{2+}$ + $2{\mathrm{e}}^{-}$ $\to$ M needs 2 ${\mathrm{e}}^{-}$ per atom, so moles of metal = 0.1/2 = 0.05 mol. Atomic mass = 2/0.05 = 40. Hence (b).