[big]

Calculate  :delta: S,  :delta: S_total, and  :delta: S_surroundings when the volume of 85.0 g of CO initially at 298 K and 1.00 bar increases by a factor of three in  an expansion against Pexternal = 0. Take C_P,m to be constant at the value 29.14 J mol–1 K–1 and assume ideal gas behavior.  State whether each process is spontaneous.

I understand that w=0 in this situation, but what about :delta: T? Why is :delta: T 0? Is it because the surroundings keep the temperature of the system constantly at 298 K?

[spankythehippo]

Entropy is a thermodynamic function which is associated with the different energy states or spatial arrangements in a system. This is completely random.

Absolute entropies are referenced to zero entropy for perfectly crystalline solids at 0K.

ΔS = S_final – S_initial

If the system had an increase in pressure, the molecules are distributed throughout a smaller volume in a gaseous state. There will be a decrease in freedom of motion. This makes ΔS negative.

In your question, I'm assuming you mean Standard Molar Entropy.

Here are some observations about S°.

• S° of elements at 298K
• S° values of gases are greater than those of liquids and solids
• S° values increase with molar mass
• S° values increase with increasing number of atoms in a substance

The ΔT values are zero. The temperature changes that occur in the system are negligible.