Question

Is the reaction exothermic or endothermic?

Answer 1

To determine whether a reaction is exothermic or endothermic, we look at the heat exchange during the process:

- A reaction is called exothermic when it releases heat to the surroundings. The temperature of the surroundings usually increases, and the enthalpy change (ΔH) is negative.

- A reaction is called endothermic when it absorbs heat from the surroundings. The temperature of the surroundings usually decreases, and the enthalpy change (ΔH) is positive.

Justification depends on observation or data:
- If the system becomes hot or heat is released (like in combustion), the reaction is exothermic.
- If the system becomes cold or absorbs heat (like in photosynthesis or dissolving ammonium chloride in water), the reaction is endothermic.

Conclusion:
To decide if a reaction is exothermic or endothermic, check the heat flow. If heat is given out, it's exothermic. If heat is taken in, it's endothermic.