Question

The mole fraction of CO2 in a certain solution with H2O as the solvent is 3.6 × 10−4. The
molality of CO2 in this solution is about:

A. 0.00036 m
B. 0.0065 m
C. 0.020 m
D. 2.0 × 10−5 m
E. 6.5 m

Answer 1

The definition of molal is
moles/kg solvent.

X_CO2 = 3.6 x 10^-4

We take 1 mole of solution. That will contain 3.6 x 10^-4 moles CO2 and 1 kg solvent. How many grams CO2 is that?
3.6 x 10^-4 moles x (44 g/mol) = 0.0158 grams. How much will the solution weigh? If we had 1000 g solvent, that + 0.0158 g solute = 1000.0158 grams total

So we have 3 6 x 10^-4 moles/1.0000158 = ?? m

Answer 2

.00036