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.
1. Based on Table 2, what is the observed i value for a 0.6 mol/kg H2O solution of (NH4)2SO4 ?
Your Answer is
Correct Answer is B
Explanation
According to Table 2, the intersection of 0.6 units H2O and (NH4)2SO4 is 2.00