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Colligative Properties. Vocabulary. Hypotonic – a cell that is placed in a solution and bursts. Raoult’s Law – states that the magnitude of vapor pressure reduction is proportional to the solution’s concentration. Isotonic – a solution where osmosis does not occur
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Vocabulary • Hypotonic – a cell that is placed in a solution and bursts. • Raoult’s Law – states that the magnitude of vapor pressure reduction is proportional to the solution’s concentration. • Isotonic – a solution where osmosis does not occur • Freezing Point - the temperature at which vapor pressure of solid and liquid phase are the same
Vocabulary • Nonvolatile – a substance that will not become a gas under existing conditions • Hypertonic – a cell that is placed in a solution and shrinks • Osmosis – the net flow of molecules from less concentrated to more concentration solutions • Boiling Point – the temperature at which vapor pressure of a liquid is equal to the eternal pressure on its surface
Boiling Point Elevation • Boiling Point Elevation – the boiling point of a liquid will be higher when another compound is added • ΔT = Kb • m • i • ΔT = change in temperature • Kb = boiling point constant for the solvent • m = molality (mol of solute ÷ kg of solvent) • i = number of ions in solute
Example #1 • What is the boiling point elevation for a solution containing 125g of ethylene glycol (C2H6O2) in 1200g of water? Kb for water = 0.52 C/m • Convert 125 g of C2H6O2 to moles. 2. Convert 1200 g of water to kg. 3. Solve for m 4. Plug into the formula ΔT = Kb • m • i
Example #2 • What is the boiling point elevation for a solution containing 125g of salt in 600g of water? Kb for water= 0.52 C/m • Convert 125 g of NaClto moles. 2. Convert 600 g of water to kg. 3. Solve for m 3. Plug into the formula ΔT = Kb • m • i
Freezing Point Depression • Freezing Point Depression - the freezing point of a liquid will be lower when another compound is added • ΔT = Kf • m • i • ΔT = change in temperature • Kf = constant for that particular solvent • m = molality (mol of solute ÷ kg of solvent) • i = number of ions in solute
Example #1 • What is the freezing point depression when 85.3g of oxygen is dissolved in 1500g of water? Kf for water = 1.86 C/m • Convert 85.3 g of oxygen to moles. 2. Convert 1500 g of water to kg. 3. Solve for m 4. Plug into the formula ΔT = Kf• m • i
Example #2 • What is the freezing point depression of a solution prepared by dissolving 11.3 g of Ca(NO3)2 in 115 g of water? Kf for water= 1.86 °C/m. • Convert 11.3 g of Ca(NO3)2 to moles. • Convert 115 g of water to kg. 3. Solve for m 4. Plug into the formula ΔT = Kf• m • i