Post on 17-Dec-2015
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Colligative Properties of Solutions
Colligative Properties of Solutions• All pure liquids have a normal freezing point.
• However, impure liquids (liquid solutions) always freeze at a LOWER temperature than normal.
• The HIGHER the concentration of impurity particles, the lower the freezing point will be.
• the impurities make it harder for the particles of the liquid to arrange themselves in the ordered structure (crystal lattice) that all solids exhibit. Thus, it takes a LOWER temperature than normal to freeze an impure liquid.
• This is called the freezing point depression of solutions.
Colligative Properties of Solutions• Rock salt or super melt are sprinkled on icy sidewalks
which lowers the ice’s freezing point.
Colligative Properties of Solutions• Glucose is a sugar which is a nonelectrolyte.• When dissolved in water, glucose does NOT form ions.• Thus a 1.00 mole of glucose dissolved in water will have
1.00 mole of dissolved particles.
C6H12O6(s) C6H12O6(aq)
C6H12O6 C6H12O6
C6H12O6 C6H12O6
OH H
OH
H
OHH
OH
H
OHH
OHH
OH
H
OH
H
OH
H
OH
H
OH H
OH H
OH H
OHH
OH H
OH
H
OHH
OH
HO
HH
OHHO
H
H
OH
H
OH
H
OH
H
OH H
OH HO
H H
OHH
C6H12O6
C6H12O6
C6H12O6
C6H12O6
[i = 1]
Colligative Properties of Solutions• Sodium chloride is a salt which is an electrolyte.• When dissolved in water, sodium chloride does form ions.• Thus a 1.00 mole of sodium chloride dissolved in water
will have 2.00 moles of dissolved particles.
NaCl(s) Na+(aq) + Cl-(aq)
Na+Cl-Na+Cl-
Cl-Na+Cl-Na+
OH H
OH
H
OHH
OH
H
OHH
OHH
OH
H
OH
H
OH
H
OH
H
OH H
OH H
OH H
OHH
OH H
OHH
OH
H
OHH
OH
HO
H
H
OH
H
OH
H
OH H
OH H
OHH
Na+
Na+
Cl-
Cl-
Cl-
Na+
Na+
Cl-
OHH
OH H
OH
H
[i = 2]
Colligative Properties of Solutions• Which of the following two solutions has more dissolved
particles? • Which of the following two solutions will have a lower
freezing point?
4.0 M C6H12O6 4.0 M NaCl
OH H
OHH
OH
H
OHH
OH
HO
H
H
OH
H
OH
H
OH H
OH H
OHH
Na+
Na+
Cl-
Cl-
Cl-
Na+
Na+
Cl-
OHH
OH H
OH
H
OH H
OH
H
OHH
OH
HO
HH
OHHO
H
H
OH
H
OH
H
OH
H
OH H
OH HO
H H
OHH
C6H12O6
C6H12O6
C6H12O6
C6H12O6
The NaCl solution!
The NaCl solution!
Colligative Properties of Solutions• When making ice cream, salt is added to the ice
surrounding the canister. The added salt lowers the ice’s melting point making the canister colder than 0oC!
Colligative Properties of Solutions• All pure liquids have a normal boiling point.
Q1: At what temperature will a pure liquid boil?
A1: The temperature at which the liquid’s vapor pressure is equal to the current air pressure.
• However, impure liquids (liquid solutions) always boil at a HIGHER temperature than normal.
• The HIGHER the concentration of impurities, the higher the boiling point will be.
• This is called the boiling point elevation of solutions.
Colligative Properties of Solutions• Coolant is added to the water in a car’s radiator which
raises the water’s boiling point.
Colligative Properties of Solutions
Ex.(1) Pure water will boil at a ____________________
temperature than saltwater.
Ex.(2) Pure water will freeze at a ____________________
temperature than saltwater.
Ex.(3) Which 1.0 M aqueous solution would have the lowest
freezing point?
(1) NaCl (2) HCl (3) KCl (4) CaCl2.
Ex.(4) If some ethylene glycol - C2H4(OH)2 is dissolved in
water, then the resulting solution will freeze at a
_______________ temperature than normal.
lower
higher
i = 2 i = 2 i = 2 i = 3
lower
Colligative Properties of Solutions• Airplane’s are deiced with ethylene glycol.
Colligative Properties of Solutions
Ex.(5) If some ethylene glycol - C2H4(OH)2 is dissolved
in water, then the resulting solution will boil at a
_______________ temperature than normal.
Ex.(6) Why will a bottle of wine (12% alc. by vol.) or beer
(3% alc. by vol.) freeze when placed in the freezer
but a bottle of gin (47% alc. by vol.) will not?
_________________________________________
_________________________________________
_________________________________________
higher
The gin has a much higher concentration of
alcohol which lowered its freezing point below
the freezer’s temperature (≈ 15oF or -10oC ).
Colligative Properties of Solutions• Gin in a freezer!