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.
3. According to Table 2, at which of the following concentrations is the observed i value for KCl the lowest ?
Your Answer is
Correct Answer is C
Explanation
According to Table 2, the lowest i value of KCl is 1.79, that is, H2O is 0.7, 0.8, and 0.9. In the question, only option C is eligible