Consider the expression below, showing the terms which contribute to the heat of solution, ΔH_soln: ΔH_soln = ΔH_solute + ΔH_solvent + ΔH_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, ΔH_soln: ΔH_soln = ΔH_solute + ΔH_solvent + ΔH_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)Δ H _solute > 0; Δ H _solvent > 0; Δ H _mix > 0 B)Δ H _solute < 0; Δ H _solvent < 0; Δ H _mix < 0 C)Δ H _solute > 0; Δ H _solvent > 0; Δ H _mix < 0 D)Δ H _solute < 0; Δ H _solvent < 0; Δ H _mix > 0 E)Δ H _solute < 0; Δ H _solvent > 0; Δ H _mix < 0

Quizplus · Accepted Answer

- ΔH_solute > 0: The heat of solute refers to the energy that is released or absorbed when a solute dissolves in a solvent. Generally, the dissolution of a solute is an endothermic process (i.e. absorbs heat from the surroundings). Therefore, ΔH_solute is usually positive. - ΔH_solvent > 0: Similarly, the heat of solvent refers to the energy that is released or absorbed when a solvent dissolves in a solute. This process is also endothermic and therefore, ΔH_solvent is positive as well. - ΔH_mix < 0: The heat of mixing refers to the energy change that occurs when two or more substances are mixed together. This process could be exothermic (i.e. releases heat) or endothermic (i.e. absorbs heat) depending on various factors such as the nature of the substances, their concentration, temperature, etc. In the case of ideal solutions (which can be approximated by dilute solutions), the heat of mixing is usually negative because the energy required to break the solute-solute and solvent-solvent interactions is smaller than the energy released by the formation of new solute-solvent interactions. Therefore, ΔH_mix is usually negative.

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