Question

Choose the system from each pair that likely has the higher entropy.

ice
liquid water

liquid water at 10°C
liquid water at 90°C
1 mol NaBr dissolved in 1 L water

1 mol solid NaBr and 1 L pure water in separate containers

3 mol N2 gas and 2 mol O2 gas in separate containers

3 mol N2 gas and 2 mol O2 gas mixed together

Answer 1

- Liquid water (higher entropy than ice). Reason: liquid molecules have more freedom of motion and many more accessible microstates than molecules locked in a crystal lattice.

- Liquid water at 90°C (higher entropy than at 10°C). Reason: entropy increases with temperature because thermal energy populates more microstates and increases molecular disorder.

- 1 mol NaBr dissolved in 1 L water (higher entropy than solid NaBr + pure water in separate containers). Reason: dissolution disperses ions throughout the solvent and increases the number of accessible arrangements (and the hydration increases microscopic disorder).

- 3 mol N2 and 2 mol O2 mixed together (higher entropy than kept in separate containers). Reason: mixing different gases increases the number of distinguishable arrangements (positive entropy of mixing).