Question
Calcium chloride (CaCl₂) has an exothermic change of solution equation. This means that when calcium chloride dissolves in water, it releases heat, causing the solution to warm up. This is indicated by a negative enthalpy change (ΔH < 0) for the solution process. how do you know?:
Answers
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GPT-4o mini
The exothermic nature of the dissolution of calcium chloride (CaCl₂) in water is confirmed through experimental observations and thermodynamic principles. Here are the reasons why we know this is the case:
1. **Temperature Change**: When CaCl₂ is added to water, the solution often becomes noticeably warmer. This temperature rise indicates that heat energy is being released into the surrounding solution, which is characteristic of exothermic reactions.
2. **Enthalpy Change (ΔH)**: In thermodynamics, the enthalpy change (ΔH) of a system during a reaction or process helps to determine whether a reaction is exothermic or endothermic. For an exothermic process, the enthalpy change is negative (ΔH < 0) because the system (here, the dissolving CaCl₂) loses heat to the surroundings.
3. **Thermodynamic Calculations**: The dissolution of salts can be quantitatively analyzed using calorimetry, where the heat released can be measured. If the measured heat is negative, it confirms that heat is released, further supporting that the ΔH for the dissolution of CaCl₂ is negative.
4. **Literature Data**: The dissolution of CaCl₂ is well-characterized in chemical literature. Standard enthalpy of solution values for various salts are commonly tabulated, and for CaCl₂, the given ΔH value is negative, indicating an exothermic process.
5. **Lattice Energy and Hydration Energy**: The dissolution process can also be explained in terms of lattice energy (the energy needed to separate the ions in the solid) and hydration energy (the energy released when ions interact with water molecules). For CaCl₂, the hydration energy is greater than the lattice energy, resulting in a net release of energy when the salt dissolves.
These points collectively demonstrate why we can conclude that the dissolution of calcium chloride in water is an exothermic reaction.
1. **Temperature Change**: When CaCl₂ is added to water, the solution often becomes noticeably warmer. This temperature rise indicates that heat energy is being released into the surrounding solution, which is characteristic of exothermic reactions.
2. **Enthalpy Change (ΔH)**: In thermodynamics, the enthalpy change (ΔH) of a system during a reaction or process helps to determine whether a reaction is exothermic or endothermic. For an exothermic process, the enthalpy change is negative (ΔH < 0) because the system (here, the dissolving CaCl₂) loses heat to the surroundings.
3. **Thermodynamic Calculations**: The dissolution of salts can be quantitatively analyzed using calorimetry, where the heat released can be measured. If the measured heat is negative, it confirms that heat is released, further supporting that the ΔH for the dissolution of CaCl₂ is negative.
4. **Literature Data**: The dissolution of CaCl₂ is well-characterized in chemical literature. Standard enthalpy of solution values for various salts are commonly tabulated, and for CaCl₂, the given ΔH value is negative, indicating an exothermic process.
5. **Lattice Energy and Hydration Energy**: The dissolution process can also be explained in terms of lattice energy (the energy needed to separate the ions in the solid) and hydration energy (the energy released when ions interact with water molecules). For CaCl₂, the hydration energy is greater than the lattice energy, resulting in a net release of energy when the salt dissolves.
These points collectively demonstrate why we can conclude that the dissolution of calcium chloride in water is an exothermic reaction.