Question

Part A

Rank these systems in order of decreasing entropy.

Rank from highest to lowest entropy. To rank items as equivalent, overlap them

1/2 mol of
neon gas at
273 K and 20 L

1/2 mol of
liquid neon
at 100 K

1/2 mol of
neon gas at
100 K and 20 L

1 mol of
fluorine gas at
273 K and 40 L

1 mol of
neon gas at
273 K and 40 L

1 mol of
neon gas at
273 K and 20 L

1 mol of
carbon disulfide gas at
273 K and 40 L

Part B

Classify each process by its individual effect on the entropy of the universe, S.

a process run infinitesimally slowly at equilibrium and reversed to its original state

a constant composition mixture of solid and liquid water at STP (273.15 K and 1 atm)

motion of a frictionless pendulum

a bag of red marbles and a bag of green marbles dumped together on a table top

evaporation of water from a cup

isothermal expansion of a real gas

Part C

Predict the sign of ΔS for each process.

H2O(g)→2H3(g)+O2(g)

I2(g)→I2(s)

the sublimation of carbon dioxide

Answer 1

(A)

Entropy is the measure of disorderness. Higher is disorder higher is the entropy.

Hence,

1. 1 mol Ne gas at 273 K and 40 L

2. 1 mol F2 gas at 273 K and 40 L

3. 1 mol CS2 gas at 273 K and 40 L

4. 1 mol Ne gas at 273 K and 20 L

5. 1/2 mol Ne gas at 273 K and 20 L

6. 1/2 mol Ne gas at 100 K and 20 L

7. 1/2 mol Ne liquid at 100 K

(C)

2 H2O (g) ------> 2 H2 (g) + O2 (g)

Number of gaseous moles increased from reactants to products, hence entropy of the reaction also increases.

deltaS = +ve

I2 (g) ---------> I2 (s)

Physical state is changed form gas to solid, hence entropy is decreased due decrease in disorder.

deltaS = - Ve