Question

Which reactants would lead to a spontaneous reaction?

Mn2+ and Cr
Fe and Cu2+
Al and Ba2+
Mg2+ and Sn

Answer 1

Answer: Option (b) is the correct answer.

Step-by-step 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.