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Colligative Properties. Chapter 14. Review. Freezing Point Temperatures and Boiling Point Temperatures are constant for pure samples of the same material (chemical) But… can be altered by mixing or adding another chemical Adding impurities. Boiling Point Elevation.
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Colligative Properties Chapter 14
Review • Freezing Point Temperatures and Boiling Point Temperatures are constant for pure samples of the same material (chemical) • But… can be altered by mixing or adding another chemical • Adding impurities
Boiling Point Elevation • An increase in boiling point temperature caused by adding another chemical (usually added to a liquid) • Example – adding salt to boiling water causes the water to boil at a temperature higher than 100 C
Calculation • Degree C change = molality of solute X Molal boiling elevation constant of the solute • Kbp • Table on page 676 • C/m
example • 0.144 g of Eugenol is added to 10.0 g of liquid benzene • Normal boiling point of benzene is 80.10 C. • What is the boiling point temperature of this mixture?
Freezing Point Depression • Lowering of the freezing point temperature by the addition of a different chemical to the solution • Adding antifreeze (ethylene glycol) to your cars radiator • Adding a chemical to a pure sample alters both the boiling and freezing temps.
Alternate example • Calculations are the same as boiling point elevation • What mass of OHCH2CH2OH (antifreeze) must be added to 5.50 KG of water to lower the freezing point of water from 0.0 to –10.0 C?