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Warm-Up 5/12/14
1) What is the formula for
molality?
2) What is the molality of 3.68
mol of sucrose (C12H22O12) in
2.50 kg of water?
Checking 5 mins after the bell
Objective
Use freezing point depression
and boiling point elevation
formulas
Agenda
Freezing Point Depression
Boiling Point Elevation
Warm-Up 5/12/14
1) What is the formula for
molality?
2) What is the molality of 3.68
mol of sucrose (C12H22O12) in
2.50 kg of water?
Checking 5 mins after the bell
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What happened?
ΔTf = Kfcm
ΔTf is change in freezing point
Kf is freezing-point depression
constant
Cm is concentration in molal.
Same effect on boiling point
ΔTb = Kbcm
ΔTb is change in boiling point
Kb is boiling-point elevation
constant
Cm is concentration in molal.
If you use 3.68 mol of sucrose and dissolve this into
2.50kg of water, what will be the change in the
freezing point of your solution. Assume the Kf of
water is -1.86oC/m.
Homework
Finish worksheet
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