Question

Consider the entropy change in the following chemical or physical processes:

1.2 Na(s) + Cl₂(g) → 2 NaCl(s)
2. N₂(g) + 3 H₂(g) → 2 NH3(g)
3. H₂O(s)→ H₂O(l)
4. C10H22(1)→ C10H22(S)
5.2 Mg(s) + O₂(g) → 2 MgO(s)
In which of these processes is entropy increased?

Answer 1

D

Step-by-step explanation:

Recall that entropy measures the number of microstates in a substance, which is highest in gases, followed by liquids and solids. Hence, entropy increases if the products have more gaseous molecules than the reactants.

• In reaction one, chlorine gas is converted into solid NaCl, so entropy decreaes.

• In reaction two, four moles of gas are converted into two moles of gas, so entropy decreases.

• In reaction three, ice is melted to form water, which has higher entropy. Thus, entropy increases.

• In reaction four, a liquid is freezed into its solid phase, leading to a decrease in entropy.

• In reaction five, oxygen gas is converted into solid MgO, so entropy decreases.

In conclusion, the answer is D.