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.
33. A chemist claimed that compounds that dissolve exothermically in water decrease in solubility as temperature increases. Is her claim supported by the data in Figures 1-3 ?
Your Answer is
Correct Answer is B
Explanation
From figure 1, it can be seen that Compound B is exothermic during the welding process. Looking at figure 3 again, as the temperature increases, the solubility of Compound B decreases. So the statement in the question stem is correct