Question

In the reactions given below, identity the species undergoing oxidation and reduction:

$A)$ $H_{2}S\left(g\right)+C{l}_2\to 2HCl\left(g\right)+S\left(s\right)$

$B)$ $3F{e}_3{O}_4\left(s\right)+8Al\left(s\right)\to 9Fe\left(s\right)+4A{l}_2{O}_3\left(s\right)$

$C)$ $2Na\left(s\right)+H_2\left(g\right)\to 2NaH\left(s\right)$

Answer 1

$A)$ $H_{2}S$ is oxidised because a more electronegative element, chlorine is added to hydrogen (or a more electropositive element, hydrogen has been removed from $S$). Chlorine is reduced due to addition of hydrogen to it.

$B)$ Aluminium is oxidised because oxygen is added to it. Ferrous ferric oxide $\left(F{e}_3{O}_4\right)$ is reduced because oxygen has been removed from it.

$C)$ With the careful application of the concept of electronegativity only we may infer that sodium is oxidised and hydrogen is reduced. Na is oxidised to $N{a}^{+}$ and hydrogen is reduced from $H_2$ and $H^{-}ion.$