Question

Which reactants would lead to a spontaneous reaction?

Answer 1

Answer: Option (b) is the correct answer.

Explanation:

The elements which have excess or deficiency of electrons will react readily.

Atomic number of Mn is 25 and electronic configuration of $Mn^{2+}$ is [Ar]$4s^{0}3d^{5}$. This configuration is stable.

Atomic number of Cr is 24 and electronic configuration of $Cr$ is [Ar]$4s^{1}3d^{5}$. This configuration is not stable.

Atomic number of Fe is 26 and electronic configuration of $Fe$ is [Ar]$4s^{2}3d^{6}$. This configuration is stable.

Atomic number of Cu is 29 and electronic configuration of $Cu^{2+}$ is [Ar]$4s^{0}3d^{9}$. This configuration is not stable.

Atomic number of Al is 13 and electronic configuration of Al is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{1}$. This configuration is not stable.

Atomic number of Ba is 56 and electronic configuration of $Ba^{2+}$ is [Kr]$4d^{10}5s^{2}5p^{6}$. This configuration is stable.

Atomic number of Mg is 12 and electronic configuration of $Mg^{2+}$ is $1s^{2}2s^{2}2p^{6}$. This configuration is stable.

Atomic number of Sn is 50 and electronic configuration of Sn is [Kr]$4d^{10}5s^{2}5p^{2}$. This configuration is stable.

Thus, we can conclude that out of the given options, only Fe and $Cu^{2+}$ reactants would lead to a spontaneous reaction as they have incomplete sub-shells. Therefore, in order to gain stability they will readily react.