Passage VI
When compounds dissolve in water, they either give off heat to, or absorb heat from, the solution. The transfer of heat (△H) is negative (exothermic) when heat is given off, or positive (endothermic) when heat is absorbed. Figure 1 shows the △H, in kilojoules per mole (kJ/mole, where 1 mole is 6 x 1023 molecules of any compound), when Compounds A or B dissolve in water at 25°C. Solubility is the maximum amount of a compound that will dissolve in a given volume of solvent. Figures 2 and 3 show how temperature affects the solubility (in moles/L) of Compounds A and B, respectively, in water.
31. According to Figures 2 and 3,Compounds A and B have the same solubility at what temperature, if any?
Your Answer is
Correct Answer is D
Explanation
Looking at figure 2, the range of solubility corresponding to Compound A is from about 0.1-1.3 moles/L, while the range of solubility corresponding to Compound B is from about 0.01-0.025 moles/L. These two ranges do not intersect