162 12. Which of the following will have the lowest and which will have the highest total vapor pressure at 25°C? a. Pure water b. A solution of sucrose in water with X 0.01 (X-mole fraction) c. A solution of KCl with X = 0.01 d. A solution of methanol in water with X = 0.2 (vapor pressure of methanol is 143 torr at 25°C). 13. Place the following solutions (in water) in order by size of freezing point depression: a) 1.0 m glucose b) 1.0 m NaCl in water c) 1.0 m HCN d) 1.0 m MgCI2 14. A liquid solution consists of 0.35 mole fraction ethylene dibromide (C,H,Br) and 0.65 mole fraction propylene dibromide (C,H.Br,). Both these liquids are volatile. Calculate the total vapor pressure of the solution assuming the solution is ideal. P(C,H,Br) -173 mmHg and P(C,H,Br,) -124 mmHg at 85°C cl andCHCL Calculate the mole fraction of Solution Ans 12 : The lowest vapor pressure : c) A solution of KCl with X = 0.01 The highest vapor pressure : d) A solution of methanol in water with X =0.2 KCl is a non volatile solute , which when added to the water dissociates into its ions (vont hoff\'s factor =2) , and causes relative lowering of vapor pressure. Methanol is a very volatile liquid having lower enthalpy of vaporizationa and weaker intermolecular forces , so the vapor pressure of the solution decreases. .

1. 162 12. Which of the following will have the lowest and which will have the highest total vapor
pressure at 25°C? a. Pure water b. A solution of sucrose in water with X 0.01 (X-mole fraction)
c. A solution of KCl with X = 0.01 d. A solution of methanol in water with X = 0.2 (vapor
pressure of methanol is 143 torr at 25°C). 13. Place the following solutions (in water) in order
by size of freezing point depression: a) 1.0 m glucose b) 1.0 m NaCl in water c) 1.0 m HCN d)
1.0 m MgCI2 14. A liquid solution consists of 0.35 mole fraction ethylene dibromide (C,H,Br)
and 0.65 mole fraction propylene dibromide (C,H.Br,). Both these liquids are volatile. Calculate
the total vapor pressure of the solution assuming the solution is ideal. P(C,H,Br) -173 mmHg and
P(C,H,Br,) -124 mmHg at 85°C cl andCHCL Calculate the mole fraction of
Solution
Ans 12 :
The lowest vapor pressure : c) A solution of KCl with X = 0.01
The highest vapor pressure : d) A solution of methanol in water with X =0.2
KCl is a non volatile solute , which when added to the water dissociates into its ions (vont hoff's
factor =2) , and causes relative lowering of vapor pressure.
Methanol is a very volatile liquid having lower enthalpy of vaporizationa and weaker
intermolecular forces , so the vapor pressure of the solution decreases.