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Raoult\'s Law tells us that in an ideal solution, the vapour pressure of a compo

ID: 699651 • Letter: R

Question

Raoult's Law tells us that in an ideal solution, the vapour pressure of a component is proportional to the mole fraction of that component in solution.

Mole fraction of sucrose: =Moles of sucrose/ Moles of sucrose + moles of water

MW (C12H22O11) = 12*12 + 22*1 + 11*16 = 342 g/mol  

MW (H2O)= 1*2+16=18g/mol

sucrose=2x10^2g/342.13gmol/2x10^2.g/342.13gmol/3.50x10^2/18.01gmol

= 0.584/20.024

=0.029

The number of moles in the mixture= 3.50x10^2/18 +2.00x10^2/342

=19.44+0.584

= 20.024

Mole fraction of water:

water=3.50x10^2g/18.01gmol/2x10^2g/342.13gmol/+350x10^2g/18.01gmol

=19.44/20.024

=

Note that by definition, sucrose+water=1

Because sucrose is involatile, the vapour pressure of the solution is proportional to the mole fraction of water:

Psolution=water×17.5mmHg

=0.9708×17.5mmHg

=16.98.mm.Hg

0.9708  

Explanation / Answer

2. The vapor pressure of water at 20°C is 17.5 mmHg. What is the vapor pressure of water over a solution prepared from 2.00x 10 g of sucrose (C12H22011) and 3.50 x 10 g water?