Colligative Properties

[loreben]

---

Members don't see this ad.

Hi SDners,
I have another question am quite stuck on and i need help with. The question is as follows:

Q) The Vapour pressure of pure water at 110 degree Celsius is 1070 torr. A solution of ethylene glycol and water has a vapour pressure of 1atm at 110 degree celsius. Assuming that Raoult's law is obeyed, what is the mole fraction of ethylene glycol in the solution?

Thanks 🙂

 

[attixx]

P(soln)=X(H20)*P(H20)

760=X(H20)*1070

X(H20)=(760)/(1070)= 0.710

X(EtGly)=1 - X(H20)=1 - 0.710= 0.290

Edit: Just for clarification, I knew a few people (including myself) that got confused thinking there are not enough variables.

Roults law is P(t) = XaP(pure)a + XbP(pure)b

I think the key is that Ethylene glycol is nonvolatile. Due to that fact, the vapor pressure remains entirely due to water, and the decrease in vapor pressure once the Ethylene glycol is added is due entirely to the reduced mole fraction of water.

Cheers!