What is the sign of ΔHsoln, and how will the temperature change when a solute dissolves with the following enthalpy changes? ΔH_solute = +56 kJ/mol, ΔH_solvent = +34 kJ/mol, ΔH_{solute-solvent} = -125 kJ/mol.

Verified step by step guidance

Step 1: Understand the concept of enthalpy of solution (ΔH_{soln}). It is the overall energy change when a solute dissolves in a solvent, and it can be calculated using the formula: ΔH_{soln} = ΔH_{solute} + ΔH_{solvent} + ΔH_{solute-solvent}.

Step 2: Identify the given enthalpy changes: ΔH_{solute} = +56 kJ/mol, ΔH_{solvent} = +34 kJ/mol, and ΔH_{solute-solvent} = -125 kJ/mol.

Step 3: Substitute the given values into the formula for ΔH_{soln}: ΔH_{soln} = (+56 kJ/mol) + (+34 kJ/mol) + (-125 kJ/mol).

Step 4: Analyze the sign of ΔH_{soln}. If the result is negative, the process is exothermic, meaning the solution releases heat and the temperature increases. If positive, the process is endothermic, meaning the solution absorbs heat and the temperature decreases.

Step 5: Calculate the sum of the enthalpy changes to determine the sign of ΔH_{soln} and predict the temperature change accordingly.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Enthalpy of Solution (ΔHsoln)

The enthalpy of solution (ΔHsoln) is the overall heat change that occurs when a solute dissolves in a solvent. It is calculated by considering the enthalpy changes associated with breaking solute-solute and solvent-solvent interactions, as well as the formation of solute-solvent interactions. A positive ΔHsoln indicates that the process is endothermic, absorbing heat, while a negative ΔHsoln indicates an exothermic process, releasing heat.

Breaking and Forming Interactions

When a solute dissolves, energy is required to break the intermolecular forces between solute particles (ΔHsolute) and solvent molecules (ΔHsolvent). This energy input is countered by the energy released when new solute-solvent interactions are formed (ΔHsolute-solvent). The balance of these energy changes determines whether the overall process absorbs or releases heat, influencing the temperature of the solution.

Temperature Change in Dissolution

The temperature change during the dissolution process is directly related to the sign of ΔHsoln. If ΔHsoln is positive, the solution absorbs heat, leading to a decrease in temperature, while a negative ΔHsoln results in heat release, causing an increase in temperature. Understanding this relationship helps predict how the dissolution of a solute will affect the thermal properties of the solution.

Recommended video:

Guided course