Introduction to Colligative Properties
Colligative properties are a set of physical properties of solutions that depend on the concentration of solute particles in the solution, rather than the identity of the solute. These properties are important in understanding the behavior of solutions and are used in various applications such as chemistry, biology, and medicine. In this article, we will explore the different types of colligative properties, their applications, and provide a worksheet with answers to help you practice.
Types of Colligative Properties
There are four main types of colligative properties:
- Boiling Point Elevation: The boiling point of a solution is higher than that of the pure solvent.
- Freezing Point Depression: The freezing point of a solution is lower than that of the pure solvent.
- Osmotic Pressure: The pressure exerted by a solution on a semipermeable membrane to prevent the flow of solvent into the solution.
- Vapor Pressure Lowering: The vapor pressure of a solution is lower than that of the pure solvent.
Boiling Point Elevation
Boiling point elevation is the increase in boiling point of a solution due to the presence of solute particles. The magnitude of boiling point elevation is directly proportional to the molality of the solution. The formula to calculate boiling point elevation is:
ΔT = Kb * m
where ΔT is the boiling point elevation, Kb is the boiling point elevation constant, and m is the molality of the solution.
Freezing Point Depression
Freezing point depression is the decrease in freezing point of a solution due to the presence of solute particles. The magnitude of freezing point depression is directly proportional to the molality of the solution. The formula to calculate freezing point depression is:
ΔT = Kf * m
where ΔT is the freezing point depression, Kf is the freezing point depression constant, and m is the molality of the solution.
Osmotic Pressure
Osmotic pressure is the pressure exerted by a solution on a semipermeable membrane to prevent the flow of solvent into the solution. The osmotic pressure of a solution is directly proportional to the concentration of solute particles and the temperature of the solution. The formula to calculate osmotic pressure is:
π = cRT
where π is the osmotic pressure, c is the concentration of solute particles, R is the gas constant, and T is the temperature of the solution.
Vapor Pressure Lowering
Vapor pressure lowering is the decrease in vapor pressure of a solution due to the presence of solute particles. The magnitude of vapor pressure lowering is directly proportional to the mole fraction of the solute. The formula to calculate vapor pressure lowering is:
ΔP = P° * X
where ΔP is the vapor pressure lowering, P° is the vapor pressure of the pure solvent, and X is the mole fraction of the solute.
Worksheet
Problem 1
A solution of glucose in water has a molality of 2.5 m. What is the boiling point elevation of the solution? (Kb = 0.51 K/m)
Answer
ΔT = Kb * m = 0.51 K/m * 2.5 m = 1.275 K
Problem 2
A solution of urea in water has a molality of 1.8 m. What is the freezing point depression of the solution? (Kf = 1.86 K/m)
Answer
ΔT = Kf * m = 1.86 K/m * 1.8 m = 3.348 K
Problem 3
A solution of NaCl in water has a concentration of 0.5 M. What is the osmotic pressure of the solution at 25°C? (R = 0.082 L-atm/mol-K)
Answer
π = cRT = 0.5 M * 0.082 L-atm/mol-K * 298 K = 12.31 atm
Problem 4
A solution of ethanol in water has a mole fraction of 0.2. What is the vapor pressure lowering of the solution? (P° = 23.76 mmHg)
Answer
ΔP = P° * X = 23.76 mmHg * 0.2 = 4.752 mmHg
👍 Note: These problems are meant to be solved using the formulas provided in the article. Make sure to check your units and calculations carefully.
Conclusion
Colligative properties are an important set of physical properties of solutions that depend on the concentration of solute particles. Understanding these properties is crucial in various applications such as chemistry, biology, and medicine. We hope this article and worksheet have helped you understand and practice colligative properties.
What is the main difference between boiling point elevation and freezing point depression?
+Boiling point elevation is the increase in boiling point of a solution due to the presence of solute particles, while freezing point depression is the decrease in freezing point of a solution due to the presence of solute particles.
What is the formula to calculate osmotic pressure?
+π = cRT, where π is the osmotic pressure, c is the concentration of solute particles, R is the gas constant, and T is the temperature of the solution.
What is the unit of osmotic pressure?
+The unit of osmotic pressure is typically measured in atmospheres (atm) or pascals (Pa).
Related Terms:
- Termokimia
- Kimia
- Reaksi kimia
- Peluruhan radioaktif
- Sifat koligatif larutan
- Colligative properties Worksheet answer key
