Which of the following is a proper use for a constant-pressure calorimeter?

• A. Measuring the enthalpy change of a chemical reaction occurring in solution
• B. Determining the melting point of a solid
• C. Calculating the pH of an acidic solution
• D. Measuring the electrical conductivity of a solution

Answer: (A)

Verified step by step guidance

1. Understand the purpose of a constant-pressure calorimeter: it is designed to measure heat changes (q) during processes occurring at constant atmospheric pressure, which directly relates to enthalpy changes (ΔH).
2. Recall that enthalpy change (ΔH) is the heat absorbed or released by a system at constant pressure, and a constant-pressure calorimeter allows direct measurement of this heat.
3. Evaluate each option: Measuring enthalpy change of a chemical reaction in solution fits perfectly because the calorimeter tracks heat flow at constant pressure during the reaction.
4. Recognize that determining melting points, calculating pH, or measuring electrical conductivity are not related to heat measurement or enthalpy changes, so these are not appropriate uses for this type of calorimeter.
5. Conclude that the proper use of a constant-pressure calorimeter is to measure the enthalpy change of a chemical reaction occurring in solution.