Question

Question #b226c

Answer 1

`K_"sp"=1.6xx10^-9`.............

Explanation:

`5C_2O_4^(2-) + 2MnO_4^(-) + 16H^(+) rarr 2Mn^(2+) + 10CO_2(g)uarr + 8H_2O`.

So, we works out moles of `"permanganate"`:

`=0.001*mol*L^-1xx4xx10^-3L=4xx10^-6*mol`

And thus, by the stoichiometry, there were `5/2xx4xx10^-6*mol` `"calcium oxalate"`, which were dissolved in `250*mL` water under conditions of saturation, i.e. a concentration of.......

`(5/2xx4xx10^-6*mol)/(0.250*L)=4.0xx10^-5*mol*L^-1`.

But, by specification, this represented a saturated solution.

And so `K_"sp"=[Ca^(2+)][C_2O_4^(2-)]`

`=(4.0xx10^-5*mol*L^-1)^2=1.6xx10^-9`