Question

Of the following processes, which are exothermic?

a. H₂O(l) → H₂O(g)
b. H₂O(g) → H₂O(l)
c. H₂O(g) → H₂O(s)
d. H₂O(s) → H₂O(g)
e. H₂O(l) → H₂O(s)
f. H₂O(s) → H₂O(l)

Answer 1

Exothermic processes release heat, like the condensation of water vapor (H₂O(g) → H₂O(l)), deposition of water vapor (H₂O(g) → H₂O(s)), and freezing of water (H₂O(l) → H₂O(s)). Endothermic processes absorb heat, such as boiling water (H₂O(l) → H₂O(g)), melting ice (H₂O(s) → H₂O(l)), and sublimation of ice (H₂O(s) → H₂O(g)).

Step-by-step explanation:

Of the processes listed, we can determine which are exothermic and which are endothermic by considering the energy flows. An exothermic process releases heat to the surrounding environment, while an endothermic process absorbs heat.

• b. H₂O(g) → H₂O(l) is exothermic because gas condensing into a liquid releases heat.
• c. H₂O(g) → H₂O(s) is exothermic because gas turning into a solid (deposition) releases heat.
• e. H₂O(l) → H₂O(s) is exothermic because liquid turning into a solid (freezing) releases heat.

a. H₂O(l) → H₂O(g), d. H₂O(s) → H₂O(g), and f. H₂O(s) → H₂O(l) are all endothermic processes because they require an input of heat to proceed, such as in boiling, melting, or sublimating.