Chemistry Problem: Calculate Molar Mass of a Compound

How can we calculate the molar mass of a compound dissolved in a solution?

Given a solution containing 20.6 g of a molecular compound dissolved in 100.0 g of water with a boiling point of 101.5 C, how do we determine the molar mass of the compound?

Calculate Molar Mass

Using the boiling point elevation equation and the provided data, we can calculate the molar mass of the compound in the solution to be 70.5 g/mol.

Understanding the Solution:

In this chemistry problem, we are dealing with colligative properties and specifically calculating the molar mass of a compound in a solution based on changes in the boiling point of water. To find the molar mass, we use the formula for boiling point elevation (ΔT = Kb x molality).

First, we determine the change in temperature (ΔT) by subtracting the boiling point of the solution with the compound (101.5 C) from the boiling point of pure water (100 C), resulting in a ΔT of 1.5 C.

Next, we calculate the molality (moles of solute per kilograms of solvent) by dividing ΔT by the Kb value for water (0.512 C/m), which gives us a molality of 2.93 m.

Finally, we find the molar mass by dividing the mass of the solute (20.6 g) by the product of molality and the mass of the solvent (100.0 g converted to kg), yielding a molar mass of 70.5 g/mol.

Therefore, by following these steps, we can determine the molar mass of the compound in the solution accurately and efficiently.