Imagine a reaction that results in a change in both volume and temperature:

(b) Has there been an enthalpy change? If so, what is the sign of ∆H? Is the reaction exothermic or endothermic?

Verified step by step guidance

1. Step 1: Identify the initial and final states of the system. Initially, the temperature is 320 K and the pressure is 1 atm. Finally, the temperature is 370 K and the pressure remains 1 atm.
2. Step 2: Recognize that an increase in temperature generally indicates that heat has been absorbed by the system.
3. Step 3: Recall that enthalpy change (∆H) is related to the heat absorbed or released at constant pressure. Since the pressure is constant at 1 atm, we can consider the enthalpy change.
4. Step 4: Determine the sign of ∆H. If the system absorbs heat, ∆H is positive, indicating an endothermic reaction. If the system releases heat, ∆H is negative, indicating an exothermic reaction.
5. Step 5: Conclude that since the temperature increased from 320 K to 370 K, the system absorbed heat, making ∆H positive and the reaction endothermic.

Key Concepts

Enthalpy Change (∆H)

Enthalpy change (∆H) is a measure of the heat content of a system at constant pressure. It indicates whether a reaction absorbs heat (endothermic, ∆H > 0) or releases heat (exothermic, ∆H < 0). In the context of the given reaction, a change in temperature suggests that heat is either absorbed or released, which directly relates to the enthalpy change.

Exothermic vs. Endothermic Reactions

Exothermic reactions release heat to the surroundings, resulting in an increase in temperature of the surroundings, while endothermic reactions absorb heat, leading to a decrease in temperature of the surroundings. The temperature increase from 320 K to 370 K in the reaction indicates that heat is being absorbed, suggesting that the reaction is endothermic.

Ideal Gas Law and Thermodynamic Principles

The Ideal Gas Law (PV=nRT) relates pressure, volume, and temperature of a gas. In this scenario, the constant pressure (1 atm) and the change in temperature imply that the volume may also change, affecting the internal energy and enthalpy of the system. Understanding these principles helps in analyzing how energy is transferred during the reaction.