Boiling Point Elevation Calculation for 0.33m Solution of NHCO in Benzene

When dealing with solutions, one of the key properties often examined is the boiling point elevation. This phenomenon occurs when a non-volatile solute is dissolved in a solvent, leading to an increase in the boiling point of the solution. This article demonstrates how to calculate the boiling point of a 0.33m solution of NHCO in benzene. We will use the formula for boiling point elevation, which involves the ebullioscopic constant (Kb), the molality of the solution (m), and the van't Hoff factor (i) if applicable.

Understanding the Formula

The formula for calculating the boiling point elevation is:

ΔTb i Kb m

Where:

ΔTb) Boiling point elevation, which is the increase in boiling point of the solution. Kb Boiling point elevation constant (ebullioscopic constant) of the solvent (benzene in this case). m Molality of the solution, which is the measure of solute concentration based on the mass of the solvent. i Van't Hoff factor, which accounts for the number of particles a solute dissociates into.

Example Calculation

Given: Molar mass of NHCO 60.0 g/mol Molality of the solution (m) 0.33 m Ebullioscopic constant of benzene (Kb) 2.53 °C/m Boiling point of pure benzene 80.1 °C

The first step is to determine the van't Hoff factor (i). For NHCO, which is a molecular solute and not dissociated in the solution, the van't Hoff factor is 1.

Step 1: Calculate the boiling point elevation (ΔTb):

ΔTb i Kb m

ΔTb 1 × 2.53 °C/m × 0.33 m

ΔTb 0.8349 °C

Step 2: Determine the boiling point of the solution:

Boiling point of the solution Boiling point of pure solvent ΔTb

Boiling point of the solution 80.1 °C 0.8349 °C

Boiling point of the solution 80.9349 °C

Therefore, the boiling point of the 0.33m solution of NHCO in benzene is approximately 80.9 °C.

Explanation of the Terms

Molality (m): Molality is the measure of solute concentration based on the mass of the solvent. It is expressed as the number of moles of solute per kilogram of solvent. In this case, 0.33 m indicates 0.33 moles of NHCO per kilogram of benzene.

Ebullioscopic constant (Kb): This is the ebullioscopic constant of the solvent. It is a measure of the degree of boiling point elevation a solution experiences when a non-volatile solute is added. For benzene, this value is 2.53 °C/m.

Van't Hoff Factor (i): If the solute dissociates into multiple particles, the van't Hoff factor accounts for this. For a non-dissociating solute like NHCO, i 1.

Conclusion

Boiling point elevation is a fundamental concept in physical chemistry, particularly in solution thermodynamics. This article has demonstrated how to calculate the boiling point of a solution using the given parameters. Understanding these principles can help in a wide range of applications, from chemical engineering to pharmaceuticals.