Calculating Molal Boiling point elevation constant HELP

[piggyxchu]

Calculating Molal Boiling point elevation constant! HELP!

So here's how I did my problem, but the answer I arrived with is wrong. I need help with this...

Carbon disulfide (CS2) boils at 46.30°C and has a density of 1.261g/mL.
When 0.250 mol of a nondissociating solute is dissolved in 400.0 mL of CS2, the solution boils at 47.46°C. What is the molal boiling point elevation constant for CS2?

Homework Statement

Normal Boiling Point: 46.3°C
0.250mol of solute
400.0mL of CS2 (solvent)

Homework Equations

ΔT$_{b}$=k$_{b}$(molality)

The Attempt at a Solution

ΔT$_{b}$=47.46-46.30=1.16°C
molality = 0.250mol/0.400kg = 0.625m

k$_{b}$= ΔT$_{b}$/molality.
k$_{b}$=1.16°C/0.625=1.856.

 

[Borek]

0.400kg

Try harder.

 

[Shayes]

Try harder.

lol word

piggy, you are given the volume and the density. you want to find the mass, so what do you do?