# chemistry

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I have a problem that states:
Find the pressure of a sample of carbon tetrachloride, CCl4 if 1.00 mol occupies 35.0L at 77.0 degress C (slightly above its normal boiling point). Assume that CCl4 obeys (a) the ideal gas law; (b) the van der Waals equation. The van der Waals constants for CCl4 are a= 20.39(L^2)(atm)/mol^2 and b= 0.1383L/mol.

I tried to do the problems and the answers I got are (a)=.814atm and (b)=.800atm but the back of the book is telling me that (a)=0.821atm an (b)=0.805. I'm not sure if i'm wrong or if the book is off.

• chemistry -

Let's do the ideal gas law one.
P = nRT/V
n = 1 mole
T = 77.0 + 273.2 = 350.2 K
V = 35.0 L
R = 0.08206 L atm/mole K
P = 0.821 atm

It looks like the book is right. I suspect that you may be using the wrong value for R or are not carrying enough significant figures. Try it again with the van der Waals equation. If you don't recall it, use the second equation at
http://en.wikipedia.org/wiki/Van_der_Waals_equation#Equation

• chemistry -

how to find the percent difference?