Question

Question #fe604

Answer 1

`"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.

`"MgCl"_ (color(red)(2)(aq)) -> "Mg"_ ((aq))^(2+) + color(red)(2)"Cl"_ ((aq))^(-)`

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

• one mole of magnesium cations, `1 xx "Mg"^(2+)`
• two moles of chloride anions, `color(red)(2) xx "Cl"^(-)`

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

`"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 color(red)(cancel(color(black)("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.