osmotic pressure

[ems5184]

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If you have a solution of 1 L of H2O with 234 g of NaCl, what is the osmotic pressure at STP? (R = 0.1 L atm/mol K)

I set it up using Pi = MRT, but I keep getting 109.2 atm, and the answer topscore gives is 218.4 atm (exactly double), anyone know why this is correct?

 

[coodoo]

If you have a solution of 1 L of H2O with 234 g of NaCl, what is the osmotic pressure at STP? (R = 0.1 L atm/mol K)

I set it up using Pi = MRT, but I keep getting 109.2 atm, and the answer topscore gives is 218.4 atm (exactly double), anyone know why this is correct?

yeah, because the equation is actually pi = MRTi where i stands for the number of ions that compund forms in an aqueous soln. nacl converts to Na+ and Cl-. now i = 2

 

[ems5184]

oh ok, thanks for that reminder, i gotta work on those small details now before the test.

 

[docline]

For some reasons, I am getting 119.2 instead of 109.2. Can someone tell me where I went wrong in solving this problem.
Thanks.

 

[bpenly]

You are multiplying (4)(0.1)(298). Use 273K.