Question

A 0.9182 g sample of CaBr2 is dissolved in enough water to give 500 ml of solution. what is the calcium ion concentration in this solution

Answer 1

First calculate the number of moles of CaBr2 given the molar mass of 199.89 g/mol.

moles CaBr2 = 0.9182 g / (199.89 g / mol) = 4.60 x 10^-3 mol

 

We see that each CaBr2 contains only 1 mole of Ca, so the moles of Ca is also:

moles Ca+ = 4.60 x 10^-3 mol

 

So the molarity of this is:

Molarity Ca+ = 4.60 x 10^-3 mol / 0.500 L

Molarity Ca+ = 9.19 x 10^-3 M