Answer
There are 0.867 moles of ions in 27.5 g of $MgCl_2$.
Work Step by Step
1. Calculate the molar mass $(MgCl_2)$:
24.31* 1 + 35.45* 2 = 95.21 g/mol
2. Calculate the number of moles $(MgCl_2)$:
$n(moles) = \frac{mass(g)}{mm(g/mol)}$
$n(moles) = \frac{ 27.5}{ 95.21}$
$n(moles) = 0.289$
3. Each $MgCl_2$ has 1 $Mg^{2+}$ ion and 2 $Cl^-$ ions; therefore, there are a total of 3 ions.
$0.289 mol (MgCl_2) \times \frac{3 ions}{1 MgCl_2} = 0.867\ mol\ of \ ions$
