calculate the number of Mg2+ ions in each mL of 0.162M(molarity) magnesium bromide

Answer 1

There are 10^-3 liters of MgBr2
There are .162*10^-3 moles therefore
In each mole there are 6*10^23 molecules
so
.162*10^-3 * 6 * 10^23 ions