Question

Question #094e3

Answer 1

I believe you need context to get proper answer. We usually calculate how many moles of ion left after particular reaction. We do it using proportions.

Answer 2

Assuming that it is in solution you calculate the number of moles of an ion by multiplying the concentration by its volume.

`c=n/v`

So `n=cv`

E.g How many moles of sodium ions are there in `20cm^3` of sodium chloride which has a concentration of `2.0 mol.dm^(-3)` ?:

`n=cv =(2.0xx20)/(1000)=0.04`

Note that I have divided by 1000 to convert. `cm^3` to `dm^3`