Posted by **Sara** on Sunday, March 7, 2010 at 8:34pm.

A solution is prepared by mixing 0.0400 mol CH2Cl2 and 0.0800 mol CH2Br2 at 25 degrees C. Assume solution is ideal, calculate the composition of the vapor (in terms of mole fractions) at 25 C. At 25 C, vaporpressure of pure CH2Cl2 and pure CH2Br2 are 133 and 11.4 torr.

- chemistry -
**DrBob222**, Sunday, March 7, 2010 at 8:44pm
Sum the moles to get total moles.

mole fraction CH2Cl2 = #moles/total moles.

mole fraction CH2Br2 = #moles/total moles.

vapor pressure CH2Cl2 = mole fraction CH2Cl2 x normal vapor pressure CH2Cl2.

vapor pressure CH2Br2 = mole fraction Ch2Br2 x normal vapor pressure CH2Br2.

Total pressure is the sum of the partial pressures of each component.

- chemistry -
**Sara**, Sunday, March 7, 2010 at 9:08pm
Thanks. My answer is still coming up wrong, thought it was sig figs, but I'm getting 43.9 and 7.52.......mole fractions are .33 and .66. What gives???

- chemistry -
**DrBob222**, Sunday, March 7, 2010 at 9:32pm
I didn't round like you did AND you short changed the s.f. You are allowed three from 0.0800 and 0.400 but you rounded to 2. I leave those extra 3s and 6s in the calculator and make the other calculations.

So I divide 0.04/0.12 = 0.3333333 and multiply on the spot by 133 to obtain 44.33 torr.

0.08/0.12 = 0.666666 and multiply on the spot by 11.4 = 7.60 (note that by rounding to 0.66 the number is 7.52 and rounding to 0.67 the number is 7.63---a big difference with just one digit). So I would add 44.33 and 7.60 = 51.93. You are allowed three s.f. and I would round that final number to 51.9 torr. Check my work.

## Answer This Question

## Related Questions

- Chemistry - A solution is prepared by mixing 0.0400 mol CH2Cl2 and 0.0700 mol of...
- chemistry - A solution is prepared by mixing 0.0433 mol CH2Cl2 and 0.0623 mol ...
- AP Chemistry - A solution is prepared by mixing 0.0200 mol CH2Cl2 and 0.0500 mol...
- Chemistry - 1. If an aqueous solution that is 0.15 M in HF has an osmotic ...
- chem - Liquids A and B form an ideal solution. A certain solution contains 25 ...
- chemistry - An Ideal solution is formed by mixing 0.26 mol of pentane (vapor ...
- Chemistry - An example of a solution that exhibits a positive deviation from ...
- Chemistry - Carbon tetrachloride (CCl4) and benzene (C6H6) form ideal solutions...
- chemistry - Pentane (C5H12) and hexane (C6H14) form an ideal solution. At 25oC ...
- chem - a solution of A (molar mass 100g/mol) and B (molar mass 1.10 x 10^2 g/mol...

More Related Questions