Question

During the disproportionation of iodine to iodide and iodate ions, the ratio of iodate and iodide ions formed in the alkaline medium is:
A. 1:5
B 5:1
C. 3:1
D. 1:3

Answer 1

Hint: The iodine is disproportionate to form iodide ion and iodate ion. Every reaction should follow the law of conservation of mass. The number of moles of the reactant on the left side of the reaction should be the same as the number of moles of the product on the right side of the reaction which means the reaction should be balanced.

Complete answer:The disproportionation reaction is a type of redox reaction where a reactant of intermediate oxidation state splits into two products, one having an oxidation state with higher value and another product with oxidation state with lower value.
In the alkaline medium, iodine is disproportionate to form iodide ion and iodate ion.
The reaction is shown below.
${I_2} + O{H^ - } \to {I^ - } + IO_3^ -$
This reaction is not balanced, to find out the ratio the reaction should be balanced.
The balanced equation is given as shown below.
$3{I_2} + O{H^ - } \to 5{I^ - } + IO_3^ -$
In this reaction, three mole of iodine react with one mole of hydroxide to give five mole of iodide ion and one mole of iodate ion.
Thus, during the disproportionation of iodine to iodide and iodate ions, the ratio of iodate and iodide ions formed in the alkaline medium is 1:5.
Therefore, the correct option is B.

Note:
Disproportionation reaction is sometimes called dismutation. The reverse reaction for the disproportionation reaction is comproportionation where a compound with lower and higher oxidation state combines to form a compound with intermediate oxidation state.