Question

Rank these systems in order of decreasing entropy.

1 mol of argon gas at 273K and 20L

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

1 mol of nitrogen gas at 273K and 40L

1 mol of argon gas at 273K and 40L

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

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

1/2 mol of liquid argon at 100K

Answer 1

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

1 mol of nitrogen gas at 273K and 40L

1 mol of argon gas at 273K and 40L

1 mol of argon gas at 273K and 20L

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

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

1/2 mol of liquid argon at 100K

The less the amount of disorder (or possible states) in the system the lower the entropy.
At the same conditions 1 mol of carbon disulfide gas at 273K and 40L  can be more disordered that 1 mol of nitrogen, because carbon disulfide gas has 3 atoms which could arrange themselves in various ways whereas nitrogen only has 2. argon atoms go around by themselves not in pairs like nitrogen so the number of possible different states are even fewer.
The smaller the volume the less the molecules can move around which also reduces the number of possible different states. In a colder gas the molecules or atoms are not so energetic and so do not occupy so many different energetic states. A liquid is more ordered than a gas, again reducing the number of different states and decreasing entropy.