The heat of solution with copper (I) sulfate is exothermic. What will happen to the temperature of the container/flask when copper (II) sulfate is added to water in the container/flask? What is the sign of the enthalpy?
The correct answer and explanation is :
When copper (II) sulfate (CuSO₄) is added to water, the temperature of the container will increase, indicating that heat is released into the surroundings. This means the process is exothermic, and the sign of the enthalpy change (ΔH) is negative.
Explanation (Approx. 300 words):
When a substance dissolves in water, the process is called dissolution, and the associated heat change is known as the enthalpy of solution (ΔH_solution). This process involves two main steps:
- Breaking the lattice structure of the solute (in this case, solid CuSO₄), which requires energy (endothermic).
- Hydration of ions, where water molecules surround and stabilize the separated ions, releasing energy (exothermic).
For copper (II) sulfate, when it dissolves in water, it dissociates into Cu²⁺ and SO₄²⁻ ions. The hydration of these highly charged ions releases a significant amount of energy—more than what is needed to break apart the ionic crystal structure of solid CuSO₄. As a result, the overall dissolution process releases more energy than it consumes, making it exothermic.
An exothermic reaction causes a temperature rise in the surroundings. In this case, the water in the container will absorb the heat released from the dissolving CuSO₄, resulting in a noticeable increase in water temperature.
The sign of enthalpy change (ΔH) for an exothermic process is negative (–ΔH) because energy is lost from the system (the dissolving substance) to the surroundings (the water).
It is important not to confuse copper (I) sulfate and copper (II) sulfate, though both may have exothermic heats of solution. The key idea remains the same: if the heat of solution is exothermic, the temperature of the solution increases, and ΔH is negative.
Answer:
- Temperature change: Increases
- Sign of enthalpy (ΔH): Negative
