Question

Perform the following calculations involving concentrations of iodate ions.

(a) The iodate ion concentration of a saturated solution of Ce(IO₃)₄ was found to be 7.35 ✕ 10⁻⁴ mol/L. Find the K_sp.

(b) Find the concentration (in M) of iodate ions in a saturated solution of Ca(IO₃)₂. (K_sp = 6.47 ✕ 10⁻⁶)

Answer 1

a)

4s = 7.35*10^-4

s = 1.84*10^-4

The salt dissolves as:

Ce(IO3)4 <----> Ce4+ + 4 IO3-

   s 4s

[IO3-] = 7.35*10^-4

So,

4s = 7.35*10^-4

s = 1.84*10^-4

Ksp = [Ce4+][IO3-]^4

Ksp = (s)*(4s)^4

Ksp = 256(s)^5

Ksp = 256(1.84*10^-4)^5

Ksp = 5.40*10^-17

Answer: 5.40*10^-17

b)

The salt dissolves as:

Ca(IO3)2 <----> Ca2+ + 2 IO3-

   s 2s

Ksp = [Ca2+][IO3-]^2

6.47*10^-6=(s)*(2s)^2

6.47*10^-6= 4(s)^3

s = 1.174*10^-2 M

[IO3-] = 2s

= 2*1.174*10^-2 M

= 2.35*10^-2 M

Answer: 2.35*10^-2 M