A solution of 1.07 g of NH₄Cl (molar mass = 53.5 g/mol) in 100 g of water freezes at - 0.677 ° C. Determine the van't Hoff factor ( i ) for this solution of NH₄Cl given the freezing point depression constant for water (k_f) is 1.86 ° C/m.

Question

Quizplus · Accepted Answer

The van't Hoff factor (i) can be calculated using the formula ΔTf = i * Kf * m, where ΔTf is the freezing point depression, Kf is the freezing point depression constant, and m is the molality of the solution. First, calculate the moles of solute (NH₄Cl) using its mass and molar mass: moles = 1.07 g / 53.5 g/mol = 0.02 moles. Then, calculate the molality (m) of the solution: molality = moles of solute / kg of solvent = 0.02 moles / 0.1 kg = 0.2 m. Given ΔTf = -0.677 °C (the negative sign indicates freezing point depression) and Kf = 1.86 °C/m, we can rearrange the formula to solve for i: i = ΔTf / (Kf * m) = 0.677 °C / (1.86 °C/m * 0.2 m) = 1.82.

A Solution of 1