Question

What is the mass in grams of `"CaCl"_2"` in a `"3 M CaCl"_2"` solution?

Answer 1

`"300 g CaCl"_2"`

Explanation:

`"Molarity"=("mol solute")/("liter of solution")`

A 3 M solution of calcium chloride contains 3 moles of the solute `"CaCl"_2` in one liter of solution. To convert 3 mol `"CaCl"_2` to mass in grams, multiply the given moles by the molar mass: `"110.978 g/mol"`.

`3color(red)cancel(color(black)("mol CaCl"_2))xx(110.978"g CaCl"_2)/(1color(red)cancel(color(black)("mol CaCl"_2)))="300 g CaCl"_2"` (rounded to one significant figure due to 3 mol)