## Sabtu, 01 Agustus 2009

### VAPOR PRESSURE

1.Which of the following aqueous solutions having the indicated mole fraction of solute should have the highest vapor pressure of water assuming ideality?
a) 0.01 X(sucrose)
b) 0.005 X(Na2SO4)
c) 0.008 X(CaCl2)
d) 0.01 X(NaCl)
e) 0.007 X(Mg(OH)2)
2.Which of the following aqueous solutions having the indicated mole fraction of solute should have the lowest vapor pressure of water assuming ideality?
a) 0.02 X(sucrose) at 15oC
b) 0.01 X(NaCl) at 50oC
c) 0.008 X(CaCl2) at 25oC
d) 0.01 X(NaCl) at 25oC
e) 0.008 X(CaCl2) at 50oC
3.Which of the following aqueous solutions having the indicated mole fraction of solute should have the highest vapor pressure of water assuming ideality?
a) 0.02 X(NaCl) at 50oC
b) 0.03 X(sucrose) at 15oC
c) 0.005 X(CaCl2) at 50oC
d) 0.02 X(NaCl) at 25oC
e) 0.005 X(CaCl2) at 25oC
4.What is the vapor pressure (atm) at 40oC of a solution that contains 3.00 moles of heptane and 5.00 moles of octane? At 40oC the vapor pressure of heptane and octane are 0.121 and 0.067 atm respectively.
a) 0.067
b) 0.080
c) 0.075
d) 0.087
e) 0.061
5.What is the total vapor pressure (mm Hg) above a solution of 50.0 g of benzene, C6H6 and 50.0 g of toluene, C7H8, at 25oC. The vapor pressures of pure benzene and toluene at this temperature are 95.1 and 28.4 mm Hg respectively. Ar: C = 12, H = 1).
a) 63.8
b) 65.0
c) 63.0
d) 64.5
e) 65.6
6.What is the total pressure at 25oC of a solution of 1.0 moles of toluene (C7H8) and 2.0 moles of benzene (C6H6) at 25oC if the vapor pressures of the pure solvents are 22 and 75 mm Hg respectively at 20oC? A: C = 12, H = 1, Cl = 35.5).
a) 49
b) 36
c) 63
d) 57
e) 41
7.If the vapor pressure of water at 90° C is 0.692 atm, then what is the vapor pressure of a solution (in atm) made by dissoving 1.00 mole of urea in 1.00 kg of water?
a) 0.692
b) 0.680
c) 0.668
d) 0.656
e) 0.634
8.The vapor pressure of CH3OH at 30oC is 160 torr. What mole fraction of glycerol, C3H5(OH)3, (a nonvolatile solute) would be required to lower the vapor pressure to 130 torr? Ar: C = 12, H = 1, O = 16).
a) 0.230
b) 0.188
c) 0.198
d) 0.168
e) 0.210
9.Ethylene glycol (C2H6O2) is only slightly volatile at 100oC. Determine the vapor pressure (torr) of water at 100oC in a solution of 1.90 x 103 g of water and 625 g of ethylene glycol. The vapor pressure of pure water is 760 torr at 100oC. (Ar; C = 12, H = 1, O = 16).
a) 671
b) 694
c) 682
d) 705
e) 712
10.Sucrose, C12H22O11 (molar mass = 342 g/.mol) is a non-volatile, nonionizing solute in water. Determine the vapor pressure lowering, Pvap, at 27°C, of a solution of 75.0 grams of sucrose dissolved in 180.0 g of water. The vapor pressure of pure water at 27°C is 26.7 torr. Assume the solution is ideal.
a) 0.585 torr
b) 0.058 torr
c) 0.573 torr
d) 5.62 torr
e) 0.548 torr