White Board Review Practicing with Colligative Properties Boiling Point Elevation Freezing Point Depression Osmotic Pressure

Freezing Point Depression Practicing with Colligative Properties 38.2 g of calcium chloride is dissolved in g of water. What is the freezing point of this solution? = Kg (1.86 C°/m)(3)  T f = 12.8 C° molal (m) © Mr. D. Scott; CHS

Boiling Point Elevation Practicing with Colligative Properties 213 g of potassium nitrate is dissolved in 95.0 g of water. What is the boiling point of this solution? = Kg (0.52 C°/m)(2)  T b = 23.1 C° molal (m) © Mr. D. Scott; CHS

Freezing Point Depression Practicing with Colligative Properties Ethylene glycol (C 2 H 6 O 2 ) is commonly used as an antifreeze solute in automobile engines where it is mixed with water. If 5.50 L (6130 g) of ethylene glycol is mixed with 5.50 L (5.50 kg) of water, what will be the freezing point of the solution? = 5.50 Kg (1.86 C°/m)(1)  T f = 33.4 C° molal (m) © Mr. D. Scott; CHS

Boiling Point Elevation Practicing with Colligative Properties 213 g of potassium nitrate is dissolved in 95.0 g of water. What is the boiling point of this solution? = Kg (0.52 C°/m)(2)  T b = 12.8 C° molal (m) © Mr. D. Scott; CHS

Boiling Point Elevation Practicing with Colligative Properties Cocaine has a molecular formula of C 17 H 21 NO 4. What is the boiling point of the mixture if 15 g are dissolved in 38 g of chloroform (NBP = 61.2°C; K b = 3.62 C°/m)? = Kg (3.62 C°/m)(1)  T b = 4.7 C° molal (m) © Mr. D. Scott; CHS (Cocaine is a non-polar molecule and is therefore NOT soluble in water.)

Osmotic Pressure Practicing with Colligative Properties A 4.0 L container is separated in the exact middle by a semi-permeable membrane. The system is filled with water and contains 100. g of a molecular solute (250 g/mol ) on one side of the membrane. The temperature of the system is 32.5 °C. What is the osmotic pressure across the membrane?  = M R T i Molarity (M) = Moles solute L solution = 100.g 2.0 L = 0.20 M  = (0.20 ) ( ) ( K) (1) = 5.0 atm © Mr. D. Scott; CHS

Osmotic Pressure Practicing with Colligative Properties A 4.0 L container is separated in the exact middle by a semi-permeable membrane. The system is filled with water and contains 50. g of a molecular solute (150 g/mol ) on one side of the membrane and 75g of molecular solute (350 g/mol ) on the other side. Temperature = 41.5 °C. What is the osmotic pressure across the membrane? Molarity (M) = Mol L = 50.g 2.0 L = 0.17 M   = (0.17 ) ( ) ( K ) ( 1 ) = 4.4 atm = 75.g 2.0 L = 0.11 M   = M R T i   = M R T i  across membrane   = (0.11 ) ( ) ( K ) ( 1 ) = 2.8 atm 4.4 atm atm 1.6 atm © Mr. D. Scott; CHS