Question

450g of an aqueous solution contains 10g urea find out molality and mole fraction

Answer 1

Answer:

Here's how you can go about solving this one.

Explanation:

The problem gives you all the information you need in order to solve for the  and mole fraction of the solution. In order to determine its , you're going to need the solution's volume.

To get the volume, you have to know what the  of the solution is. Determine the  of the solution first

%w/w=msolutemsolution⋅100

In your case, the mass of the solution will be

msolution=mglucose+mwater

msolution=20+150=170 g
ρ=1.045 g/mL

Use glucose's molar mass to determine how many moles you have

20g⋅1 mole glucose180.16g=0.111 moles glucose

The solution's volume will be

170g⋅1 mL1.045g=162.7 mL

This means that its is - do not forget to convert the volume to liters!

C=nV=0.111 moles162.7⋅10−3L=0.68 M

A solution's  is defined as the number of moles of divided by the mass of the s- in kilograms! This means that you have

b=nmwater=0.111 moles150⋅10−3kg=0.74 molal

To get  fraction of sucrose, you need to know how many moles of water you have present. Once again, use water's molar mass

150g⋅1 mole water18.02g=8.24 moles water
means
The total number of moles the solution contains is

ntotal=nglucose+nwater

ntotal=0.111+8.24=8.351 moles

This means that the mole fraction of sucrose, which is defined as the number of moles of sucrose divided by the total number of moles in the solution, will be

χsucrose=nsucrosentotal=0.111moles8.351moles=0.013