SKL (2)| Kenaikan Titik Didih (∆Tb) | Penurunan Titik Beku (∆Tf)

Introduction

This tutorial provides an overview of colligative properties of solutions, specifically focusing on the boiling point elevation (kenaikan titik didih) and freezing point depression (penurunan titik beku). These concepts are fundamental in chemistry, especially in the study of solutions in high school curriculum. Understanding these properties helps in various applications, from cooking to industrial processes.

Step 1: Understanding Colligative Properties

Colligative properties depend on the number of solute particles in a solution, not on the identity of the solute. The four main colligative properties are:

• Boiling point elevation
• Freezing point depression
• Vapor pressure lowering
• Osmotic pressure

Practical Tips

• Remember that adding a solute to a solvent alters its physical properties.
• Focus on the relationships between the concentration of solute and the changes in boiling and freezing points.

Step 2: Boiling Point Elevation

Boiling point elevation occurs when a non-volatile solute is added to a solvent, causing the boiling point to increase.

Formula

The boiling point elevation can be calculated using the formula: [ \Delta T_b = i \cdot K_b \cdot m ] Where:

• ( \Delta T_b ) is the boiling point elevation
• ( i ) is the van 't Hoff factor (the number of particles the solute breaks into in solution)
• ( K_b ) is the ebullioscopic constant of the solvent
• ( m ) is the molality of the solution

Steps to Calculate Boiling Point Elevation

1. Determine the molality of the solution.
2. Find the ebullioscopic constant for the solvent.
3. Identify the van 't Hoff factor for the solute.
4. Plug the values into the formula to find ( \Delta T_b ).
5. Add ( \Delta T_b ) to the solvent's normal boiling point to find the new boiling point.

Common Pitfalls

• Ensure you correctly identify the van 't Hoff factor, as it varies for different solutes.
• Double-check the units used in calculations to avoid errors.

Step 3: Freezing Point Depression

Freezing point depression is the decrease in the freezing point of a solvent when a solute is dissolved in it.

Formula

The freezing point depression can be calculated using the formula: [ \Delta T_f = i \cdot K_f \cdot m ] Where:

• ( \Delta T_f ) is the freezing point depression
• ( i ) is the van 't Hoff factor
• ( K_f ) is the cryoscopic constant of the solvent
• ( m ) is the molality of the solution

Steps to Calculate Freezing Point Depression

1. Determine the molality of the solution.
2. Find the cryoscopic constant for the solvent.
3. Identify the van 't Hoff factor for the solute.
4. Use the formula to calculate ( \Delta T_f ).
5. Subtract ( \Delta T_f ) from the solvent's normal freezing point to find the new freezing point.

Common Pitfalls

• Similar to boiling point elevation, ensure accurate calculations of molality and constants.
• Watch for the signs in the calculations, as freezing point depression results in a lower temperature.

Conclusion

Understanding boiling point elevation and freezing point depression is crucial in various fields, including chemistry and cooking. By mastering these calculations, you can predict how solutes affect the physical properties of solvents. For further study, consider exploring the other colligative properties like vapor pressure lowering and osmotic pressure. You can also check the additional resources provided in the video description for deeper insights into colligative properties.