Passage I

The freezing point of an aqueous solution (Tf), in °C, can be calculated using the equation

Tf = −1.86 × m × i

where m is the concentration of the solute in moles of solute per kilogram of H2O (mol/kg H2O) and i is the average number of particles produced by 1 formula unit of the solute when the formula unit dissolves in H2O. The theoretical i value of a solute is the total number of particles produced when 1 formula unit of the solute dissolves in H2O. Table 1 gives, for 4 ionic compounds, the chemical formula and the theoretical i value. Table 2 shows how the observed i value at 25°C for these compounds changes with solute concentration.

Table 2 adapted from B. A. Kunkel, “Comments on ‘A Generalized Equation for the Solution Effect in Droplet Growth.’ ” ©1969 by American Meteorological Society.

5. Consider the following substances: sodium chloride, potassium chloride, magnesium chloride, ammonium sulfate, and water. Which of these substances would be classified as a solvent in the solutions represented in Table 2 ?

Answer and Explanation

Your Answer is

Correct Answer is B

Explanation

This question examines the prerequisites of Table 2, and it is necessary to distinguish the solvent. According to the text background information, i is the average number ... formula unit dissolves in H2O, so the solvent is H2 O