Ethanol has an enthalpy of vaporization of 42.3 kJ/mol. The compound has a press

Question

Ethanol has an enthalpy of vaporization of 42.3 kJ/mol. The compound has a pressure of 1.00 atm at 78.3 degree C. At what temperature is the vapor pressure equal to 1.350 atm? At what temperature is the vapor pressure equal to 1.350 atm? one beaker 20.0 g of sucrose was added to 1000 g of water and lo a second beaker 20.0 g of ethylene glycol was added to 1000 g of water? What is the vapor pressure of the sucrose solution at 50 degree C? What is the vapor pressure of the ethylene glycol solution at 50 degree C?

Explanation / Answer

Vapour pressure varies with temperature as p(T) = A*exp(-Hv/RT) where A is a constant.

At T1=78.3C=351.45K, p1=A*exp(-Hv/RT1).

At T2, ln(p2)=A*exp(-Hv/RT2).

p2/p1=exp(-Hv/RT2+Hv/RT1)

ln(p2/p1)=(Hv/R)(1/T1-1/T2).

ln(p2/p1)=ln(1.350/1)=- 0.30010459245

(Hv/R)=42300/8.31= 5090.25270758

So,

(1/351.45-1/T2)=-0.3001 /5090.25=-0.00058955...

1/T2=1/351.45+0.00058955= .0029043108

T2=344.32K = 71.2 deg C

Answer 2)

The vapor pressure will vary as the mole fraction varies.

moles H2O in each case = 1000 g x 1 mol/18 g = 55.6 moles

moles of sucrose = 20 g x 1 mol/342 g = 0.058 moles sucrose

moles of ethylene glycol = 20 g x 1 mol/62 g = 0.32 moles EG

For sucrose soln, mole fraction of H2O = 55.6/55.6 + 0.058 = 0.9989

vapor pressure of sucrose solution is =0.9989 x 0.1218 atm= .1217 atm

2) For EG soln, mole fraction of H2O = 55.6/55.6 + 0.32 = 0.9943

vapor pressure of ethylene glycol solution is =0.9943 x 0.1218 atm= .1211 atm

Related Questions

Navigate

• Browse (All)
• Browse E
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.