d- and f-Block Elements · Question 3

The number of moles of potassium iodide required to produce two moles of P is .

Answer

2

Solution

[Fe(CN)6]3- oxidises I- to I2 and is reduced to ferrocyanide:

2K3[Fe(CN)6] + 2KI 2K4[Fe(CN)6] + I2

P = K4[Fe(CN)6]; in strong acid the equilibrium lies completely towards P.

2 mol P need 2 mol KI.

(If the iodine is taken as triiodide, 2K3[Fe(CN)6] + 3KI 2K4[Fe(CN)6] + KI3, 3 mol KI are used.)

Answer: 2