Question #fe604

1 Answer
Mar 3, 2017

Answer:

#"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.