Question

Question #07b8f

Answer 1

`"0.75 moles BaCl"_2`

Explanation:

A solution's molality is simply a measure of how many moles of solute you get for every `"1 kg"` of solvent.

In your case, a `"3.0 m"` barium chloride solution will contain `3.0` moles of barium chloride, your solute, for every `"1 kg"` of water, your solvent.

You can thus use the molality of the solution as a conversion factor to help you figure out how many moles of solute you need to have in

`250 color(red)(cancel(color(black)("g"))) * "1 kg"/(10^3color(red)(cancel(color(black)("g")))) = "0.250 kg"`

of water in order to have a `"3.0 m"` solution. You can thus say that you need

`0.250 color(red)(cancel(color(black)("kg water"))) * overbrace("3.0 moles BaCl"_2/(1color(red)(cancel(color(black)("kg water")))))^(color(blue)("= 3.0 m")) = color(darkgreen)(ul(color(black)("0.75 moles BaCl"_2)))`

The answer is rounded to two sig figs.