# Vapor Pressure problem

1. Sep 22, 2008

### ally1h

1. The problem statement, all variables and given/known data
Benzene, C6H6, has a boiling point of 80 degrees Celsius. The density of benzene vapor in equilibrium with liquid benzene at 50 degrees Celsius is 1.153 g/L. What is the vapor pressure of benzene in mmHg at 50 degrees Celsius?

2. Relevant equations
PV=nRt
density = m/v

3. The attempt at a solution
I thought PV=nRt might cover it.. substituting d=mv into the equation and getting:
P = dRt/m
Plugging in I get:
[(1.153 g/L)(62.364 L Torr/mol K)(323 K)] / (1084.1 g/mol)
P = 21.43 Torr = 0.028 mmHg

What am I doing wrong? My professor covered what vaporization is, not how to go about getting vaporization pressure. I have a test Wednesday and I don't know how to do any of it!

2. Sep 22, 2008

### GCT

d = m / v

3. Sep 22, 2008

### ally1h

Sorry, that was a typo. I did divide when doing the actual problem. But I'm still not getting the answer. I forgot to add the choices on our homework handout.

a) 298
b) 50
c) 352
d) 462
e) 0.392

4. Sep 22, 2008

### GCT

What are the units in the answers?

5. Sep 23, 2008

### Staff: Mentor

What is molar mass of benzene?

6. Sep 23, 2008

### ally1h

The homework problem didn't give units for the answer so I have no clue. So I have no clue as to what to aim for. The molar mass of Benzene is 78.108 g/mol.

7. Sep 23, 2008

### ally1h

Oh! Wow, duh, I feel stupid. I calculated the molar mass incorrectly. Haha, I've got the correct answer now! It's choice A, 298!

haha, thanks for pointing out my mistake!