Oxidation reaction involves loss of electrons, and reduction reaction involves gain of electrons. The reaction in which a species disproportionates into two oxidation states (lower and higher) is called disproportionation reaction.
Which of the following statements is correct?

Options

A. An element in the lowest oxidation state acts only as a reducing agent.
B. An element in the highest oxidation state acts only as a reducing agent
C. The oxidation number of V in `Rb_4 K(HV_(10) O_(28))` is +4.
D. The oxidation number and valency of Hg in calomel is +1.

Answer

A

Explanation

A An element in the lowest oxidation state can only attain higher oxidation state. So it is a reductant and undergoes oxidation.
Calomel is `Hg_2 Cl_2`. The oxidation number of Hg is +1 and valency is 2.