Question #07b8f

1 Answer
Feb 17, 2017

Answer:

#"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.