Entropy and the direction of change

Question 1

What is the first law?

Answer 1

Energy is overall conserved

Question 2

What is the equation for the first law?

Answer 2

ΔUsystem + ΔUsurr = 0

Question 3

What is entropy?

Answer 3

Measure of disorder

Question 4

Is higher entropy or lower entropy favoured?

Answer 4

Higher

Question 5

What is the definition of spontaneous?

Answer 5

A spontaneous process corresponds to an increase in the total amount of entropy

Question 6

What is the second law?

Answer 6

Entropy may be created but not destroyed

Question 7

What is the equation to work out the change in entropy?

Answer 7

ΔS >_ q/T

Question 8

What is the equation to work out the change in entropy at a constant pressure?

Answer 8

ΔS = ΔH / T

Question 9

What is reversibility?

Answer 9

Both system and surroundings can be returned to their initial states

Question 10

What is the equation for the change in entropy during gas expansion?

Answer 10

ΔS = nRln Vf / Vi

Question 11

What equation is used for the change in entropy during heating?

Answer 11

ΔS = nCpm ln Tf/Ti

Question 12

What equation is used for the change in entropy during heating when volume is constant?

Answer 12

ΔS = nCvm ln Tf / Ti

Question 13

What equation is used to calculate entropy changes during phase transitions?

Answer 13

ΔS = ΔfusH / T

Question 14

During phase transition, what is the entropy gained by the ice equal to?

Answer 14

Entropy lost by the surroundings

Question 15

What is Trouton’s rule?

Answer 15

Vaporization produces a large entropy change because the gas is much more disordered than the liquid

Question 16

What is the value of ΔvapS?

Answer 16

85 J K-1 mol-1

Question 17

What is the equation for ΔvapH?

Answer 17

ΔvapH ≃ 85 x Tb

Question 18

What is the third law?

Answer 18

The entropy of a perfect crystalline substance is zero at absolute zero

Question 19

What is the equation to work out reaction entropies?

Answer 19

ΔrxnS = ΣvSm(products) - Σ vSm(reactant)