Consider the expression below, showing the terms which contribute to the heat of solution, $\Delta$ H_soln: $\Delta$ H_soln = $\Delta$ H_solute+ $\Delta$ H_solvent+ $\Delta$ H_mix
Which of the following sets correctly shows the signs (positive or negative) of the three terms on the right hand side of the equation?

Question

Consider the expression below, showing the terms which contribute to the heat of solution, $\Delta$H_soln: $\Delta$H_soln = $\Delta$H_solute+ $\Delta$H_solvent+ $\Delta$H_mix Which of the following sets correctly shows the signs (positive or negative) of the three terms on the right hand side of the equation? A) .$\Delta$H_solute> 0; $\Delta$H_solvent> 0; $\Delta$H_mix> 0 B) .$\Delta$H_solute< 0; $\Delta$H_solvent< 0; $\Delta$H_mix < 0 C) .$\Delta$H_solute> 0; $\Delta$H_solvent> 0; $\Delta$H_mix< 0 D) .$\Delta$H_solute< 0; $\Delta$H_solvent< 0; $\Delta$H_mix> 0 E) .$\Delta$H_solute< 0; $\Delta$H_solvent> 0; $\Delta$H_mix< 0

Quizplus · Accepted Answer

According to the expression, the three terms are the heat of solution of solute, heat of solution of solvent, and the heat of mixing. 
Heat of solution of solute refers to the energy released or absorbed when the solute dissolves in the solvent. Generally, this process is exothermic, causing the temperature of the solution to rise. Therefore, the sign of this term is expected to be positive.
Heat of solution of solvent, on the other hand, refers to the energy absorbed when the solvent dissolves in the solute. This process is generally endothermic, causing the temperature of the solution to decrease. Therefore, the sign of this term is expected to be positive.
Heat of mixing refers to the energy changes that occur when two substances are mixed. Depending on the nature of the substances and the mixing process, this energy change can be positive or negative. 
Therefore, the best choice is C as it shows that the heat of solution of both solute and solvent is positive, while the heat of mixing is negative.

Consider the Expression Below, Showing the Terms Which Contribute to the Heat