R1.4 Entropy and spontaneity

Question 1

entropy (S)

Answer 1

a measure of the dispersal or distribution of matter and/or energy in a system

Question 2

entropy is higher

Answer 2

the more ways the energy/matter can be distributed

Question 3

under the same conditions, which state has the greatest entropy

Answer 3

gas>liquid>solid

Question 4

comment on the entropy and disorder of a solid

Answer 4

low

Question 5

comment on the entropy and disorder of a gas

Answer 5

high

Question 6

entropy of a perfectly ordered crystal at 0K, explain this entropy

Answer 6

entropy = 0
there is only one way to organise it

Question 7

microstate / microscopic state

Answer 7

each of the possible arrangements

Question 8

is entropy positive or negative, explain

Answer 8

positive
everything has entropy (apart from a crystal at 0K)

Question 9

2nd law of thermodynamics

Answer 9

in every process, the total entropy of an isolated system always increases

Question 10

what does the 2nd law of thermodynamics tell us

Answer 10

it is far more likely for the universe to tend towards disorder than it is to miraculously order itself

Question 11

spontaneous reactions, comment on their entropy

Answer 11

overall increase in entropy

Question 12

overall entropy of universe unchanged

Answer 12

system at equilibrium

Question 13

negative entropy change

Answer 13

reverse process is spontaneous

Question 14

entropy of products > entropy of reactants

Answer 14

change in entropy = positive

Question 15

entropy of reactants > entropy of products

Answer 15

change in entropy = negative

Question 16

low entropy value example

Answer 16

solid at low temperature
regularly arranged lattice

Question 17

high entropy value example

Answer 17

gas at high temperature

Question 18

larger molecule has…

Answer 18

more entropy

Question 19

entropy of a closed system can…

Answer 19

remain fixed or increase

Question 20

a spontaneous reaction is one…

Answer 20

which moves to completion with no external intervention

Question 21

Gibbs free energy

Answer 21

is used to work out if a reaction is feasible at a certain temperature

Question 22

feasibility

Answer 22

the likelihood of a reaction to occur
temperature affect this

Question 23

Gibbs free energy in a feasible reaction

Answer 23

negative

Question 24

Gibbs free energy is a measure of

Answer 24

how much energy there is in a system and how feasible a reaction is

Question 25

change in entropy is a measure of

Answer 25

how energy/matter spreads out over a course of reactions

Question 26

what do we want in terms of entropy and enthalpy

Answer 26

• maximise entropy: things like to be spread out
• minimise enthalpy: things like to be low energy, more stable

Question 27

link between feasibility and temperature

Answer 27

feasibility increases with temperature

Question 28

at a constant pressure, a change is spontaneous if…

Answer 28

change in Gibbs free energy is negative

Question 29

what happens to Gibbs free energy as a reaction approaches equilibrium

Answer 29

Gibbs free energy becomes less negative and finally reaches zero