Question

butanol thermodynamics
entropy
consider the thermodynamics of the
combustion of butanol.

\\(\ce{c4h9oh(l) + 6o2(g) -> 4co2(g) + 5h2o(g)}\\)

statement i
the entropy increases. the number of
moles of gas particles increases, resulting
in more potential microstates.

statement ii
the entropy increases. the product
molecules are less complex.

statement iii
the entropy decreases. the reactant
molecules are more complex.

statement iv
the entropy decreases. the phase change
results in a smaller number of microstates.

which statement identifies the change in
entropy and the correct justification?

• statement iv
• statement i
• statement iii
• statement ii

Explanation:

To determine the entropy change, analyze the moles of gas: reactants have 6 mol of \(O_2(g)\), products have \(4 + 5 = 9\) mol of gas (\(CO_2(g)\) and \(H_2O(g)\)). Entropy (\(S\)) relates to microstates; more gas moles mean more microstates (higher \(S\)). Statement I says entropy increases (correct, gas moles increase) and justifies with more microstates. Statement II’s “less complex” is irrelevant. Statements III/IV say entropy decreases (incorrect, gas moles increase). So Statement I is correct.

Answer:

B. Statement I