Applications of Thermodynamics

I, II, and III

I and II

I only

II and III only

Only in the products side!

No!

Only in the reactants side!

Yes!

G

H

S

Q

The recrystallization process below the melting point leads to greater disorder due to defects within the crystal lattice structure.

Particles have greater freedom of movement above the melting point than at absolute zero where they are fixed in place.

At absolute zero, there are more microstates accessible making the entropy lower than when the substance is melted.

Particles exhibit stronger intermolecular forces at absolute zero leading to higher order and decreased randomness compared to above melting points.

The entropy remains constant since there is no exchange of heat or work with the surroundings.

The entropy decreases due to a decrease in temperature associated with expansion into a vacuum.

The entropy increases due to an increase in pressure that occurs upon expanding into a larger volume.

The entropy increases because the gas molecules have more microstates available in the larger volume.

Sodium chloride (NaCl) solution freezing because it goes from less ordered liquid state to a more ordered solid state.

Carbon dioxide subliming because its molecules go from solid directly into a gaseous state without becoming a liquid first.

Iodine crystals (I2), because solid to liquid transition leads to increased molecular motion and disorder.

Ethanol evaporating because it involves a phase change from liquid with some order to vapor with complete disorder.

Entropy stays constant but internal energy decreases since temperature is kept constant throughout the process and no heat is absorbed or released.

No change to entropy occurs during free expansion into a vacuum because it is an equilibrium process that does not increase the disorder of the system.

Entropy increases because the gas particles spread out into more available space, increasing disorder.

Entropy decreases since the gas does not do any work on its surroundings during the expansion, so energy dispersal is minimized.

Condensation of Steam (H2O vapor)

Solidification of Sodium Chloride (NaCl)

Freezing of Water (H2O)

Sublimation of Iodine (I2)

Compressing Nitrogen Gas at Constant Temperature

Condensation of steam into liquid water under standard conditions

Freezing water into ice under standard conditions

Evaporation of water into vapor under standard conditions

Increasing temperature generally favors spontaneity as the increased T∆S term can outweigh the positive enthalpy change (ΔH>0).

Heating usually has no effect on endothermic reactions since the overall free energy change (ΔG) remains constant regardless of temperature.

Following an increase of temperature, the spontaneity is reduced because the absolute value of T∆S decreases relative to H. (ΔH>0).

When the temperature rises, the spontaneity is enhanced due to a decrease in H which becomes more negative with increased temperatures. (ΔH>0).