Question

A student wishes to reduce the zinc ion concentration in a saturated zinc iodate solution to `1 xx 10^-6` M. How many moles of solid `KIO_3` must be added to 1.00 L of solution? [`K_(sp) Zn(IO_3)_2 = 4 xx 10^-6` at 25°C)?

Answer 1

So this is a `K_"sp"` problem, for which you have provided the relevant data...

Explanation:

We address the equilibrium...

`Zn(IO_3)_2(s) rightleftharpoonsZn^(2+)+2IO_3^(-)`...

for which `K_"sp"=[Zn^(2+)][IO_3^(-)]^2-=4.0xx10^-6`...

We will be requiring that `Zn^(2+)-=1.0xx10^-6*mol*L^-1` by the terms of the question...and thus we solve for `[IO_3^(-)]` in the given equation.....

`[IO_3^(-)]=sqrt(K_"sp"/[[Zn^(2+)]])=sqrt((4.0xx10^-6*mol*L^-1)/(1.0xx10^-6*mol*L^-1))`

`sqrt4=2*mol`...I must be clever cos I did this all in my nut!