Question #9c6af
1 Answer
Explanation:
In order to be able to calculate the molality of the solution, you need to know the number of moles of solute present for every
In your case, you know that this solution is
If you take a
#overbrace("100 g ")^(color(blue)("mass of solution")) - overbrace("16 g")^(color(blue)("mass of solute")) = overbrace("84 g")^(color(blue)("mass of solvent"))#
of water, the solvent.
You can use the composition of the sample to determine the mass of urea present in
#10^3 color(red)(cancel(color(black)("g water"))) * "16 g urea"/(84color(red)(cancel(color(black)("g water")))) = "190.48 g urea"#
To convert this to moles, use the molar mass of urea
#190.48 color(red)(cancel(color(black)("g urea"))) * "1 mole urea"/(60.06color(red)(cancel(color(black)("g urea")))) = "3.17 moles urea"#
So, you know that your solution will contain
#color(darkgreen)(ul(color(black)("molality = 3.2 mol kg"^(-1))))#
The answer is rounded to two sig figs, the number of sig figs you have for the solution's percent concentration.