# Question #fe604

Mar 3, 2017

$\text{0.336 moles}$

#### Explanation:

The trick here is to realize that magnesium chloride is soluble in water, which implies that it dissociates completely to produce magnesium cations and chloride anions.

${\text{MgCl"_ (color(red)(2)(aq)) -> "Mg"_ ((aq))^(2+) + color(red)(2)"Cl}}_{\left(a q\right)}^{-}$

Notice that every $1$ mole of magnesium chloride that dissolves in water produces

• one mole of magnesium cations, $1 \times {\text{Mg}}^{2 +}$
• two moles of chloride anions, $\textcolor{red}{2} \times {\text{Cl}}^{-}$

This tells you that for every mole of magnesium chloride that you dissolve in water, you get

$\text{1 mole Mg"^(2+) + color(red)(2)color(white)(.)"moles Cl"^(-) = "3 moles ions}$

in the resulting solution. In your case, $0.112$ moles of magnesium chloride will dissociate to produce

$0.112 \textcolor{red}{\cancel{\textcolor{b l a c k}{\text{moles MgCl"_2))) * "3 moles ions"/(1color(red)(cancel(color(black)("mole MgCl"_2)))) = color(darkgreen)(ul(color(black)("0.336 moles ions}}}}$

The answer is rounded to three sig figs.