Entropy - O

Question 1

What do all ions involve a change in

Answer 1

enthalpy and entropy

Question 2

Entropy symbol and units

Answer 2

S, JK⁻¹mol⁻¹

Question 3

Solid - liquid - gas, what happens to entropy

Answer 3

it increases because it becomes more disorderly as there are more possible positions in a gas

Question 4

Mixtures - pure substances, what happens to entropy

Answer 4

it decreases as less variations in positions

Question 5

Low number of particles - high number of particles, what happens to entropy

Answer 5

it increases

Question 6

Large molecules - small molecules, what happens to entropy

Answer 6

it decreases as more ways of arranging electrons

Question 7

Entropy definition

Answer 7

a measure of the number of ways of arranging the particles and their quanta of energy

Question 8

How to estimate the change in entropy in a reaction

Answer 8

• first look at state symbols
• then look at number of moles of each substance

Question 9

If entropy decreases, change in entropy is (+/-)

Answer 9

change in entropy is negative

Question 10

If entropy increases, change in entropy is (+/-)

Answer 10

change in entropy is positive

Question 11

N₂₍₉₎ + 3H₂₍₉₎ -> 2NH₃₍₉₎, estimate the change in entropy

Answer 11

entropy has decreased, △S = -, as everything is a gas but the number of moles has decreases from 4 to 2, so fewer ways of arranging the particles in the products.

Question 12

CaCO₃₍ₛ₎ -> CaO₍ₛ₎ + CO₂₍₉₎, estimate the change in entropy

Answer 12

entropy has increased, △S = +, because it has gone from a solid to a solid and gas so larger number of ways of arranging the particles in a gas than solid

Question 13

Equation of △Sₛᵧₛ

Answer 13

△Sₛᵧₛ = ΣS products - ΣS reactants

Question 14

Equation of △Hₛᵧₛ

Answer 14

△Hₛᵧₛ = Σ△Hθf products - Σ△Hθf reactants
https://study.com/cimages/multimages/16/enthalpy_of_formation_1.png

Question 15

△Sₜₒₜₐₗ definition

Answer 15

when a reaction occurs the entropy of surrounding is also affected, as temp increases or decreases

Question 16

Equation of △Sₜₒₜₐₗ (simple)

Answer 16

△Sₜₒₜₐₗ = △Sₛᵧₛ + △S surroundings

Question 17

What does △Sₜₒₜₐₗ have to be for a reaction to occur

Answer 17

△Sₜₒₜₐₗ must be positive for a reaction to be feasible

Question 18

Equation of △Sₜₒₜₐₗ

Answer 18

△Sₛᵧₛ - ((△Hₛᵧₛ x 1000)/temp in kelvin)

Question 19

Equation of △S surroundings

Answer 19

(- (△Hₛᵧₛ x 1000)/temp in kelvin))

Question 20

If △Sₜₒₜₐₗ is positive … (doesn’t say)

Answer 20

the reaction if feasible at that temperature but it doesn’t tell us how fast the reaction is (still need to provide activation energy)

Question 21

Steps to find if a reaction is feasible with △Hₛᵧₛ and △Sₛᵧₛ

Answer 21

1. write a balanced equation
2. calc △Sₜₒₜₐₗ
3. suggest if feasible

Question 22

How to calculate the temperature at which a reaction becomes feasible

Answer 22

if △Sₜₒₜₐₗ is zero then △Sₛᵧₛ = (△Hₛᵧₛ x 1000)/temp in kelvin)
so temp = (△Hₛᵧₛ x 1000)/△Sₛᵧₛ)

Question 23

If △Sₛᵧₛ = + and △Hₛᵧₛ = -, will the reaction occur

Answer 23

the reaction will always happen

Question 24

If △Sₛᵧₛ = - and △Hₛᵧₛ = +, will the reaction occur

Answer 24

the reaction will never happen

Question 25

If △Sₛᵧₛ = + and △Hₛᵧₛ = +, will the reaction occur

Answer 25

the feasibility depends on temperature

Question 26

If △Sₛᵧₛ = - and △Hₛᵧₛ = -, will the reaction occur

Answer 26

the feasibility depends on temperature

Question 27

What +/- do △Sₛᵧₛ and △Hₛᵧₛ need to be for a reaction to always occur

Answer 27

△Sₛᵧₛ = + and △Hₛᵧₛ = -

Question 28

What +/- do △Sₛᵧₛ and △Hₛᵧₛ need to be for a reaction to never occur

Answer 28

△Sₛᵧₛ = - and △Hₛᵧₛ = +

Question 29

What +/- do △Sₛᵧₛ and △Hₛᵧₛ need to be for a reaction to depend on temperature

Answer 29

△Sₛᵧₛ = + and △Hₛᵧₛ = + or △Sₛᵧₛ = - and △Hₛᵧₛ = -

Question 30

Why does a reaction depend on temperature if △Sₛᵧₛ = + and △Hₛᵧₛ = +

Answer 30

as △Sₜₒₜₐₗ = △Sₛᵧₛ - (△Hₛᵧₛ x 1000)/temp in kelvin) then △Sₜₒₜₐₗ = positive - (positive/temp) so as temp increases △Hₛᵧₛ/temp becomes smaller so more likely △Sₜₒₜₐₗ is to be positive

Question 31

If both △Sₛᵧₛ and △Hₛᵧₛ are positive what temp is more likely to be feasible

Answer 31

more likely to be feasible as temp increases, so △Sₛᵧₛ > △Hₛᵧₛ/temp

Question 32

Why does a reaction depend on temp if △Sₛᵧₛ = - and △Hₛᵧₛ = -

Answer 32

as △Sₜₒₜₐₗ = △Sₛᵧₛ - (△Hₛᵧₛ x 1000)/temp in kelvin) then △Sₜₒₜₐₗ = negative + (positive/temp) so as temp increases △Hₛᵧₛ/temp becomes smaller so less likely △Sₜₒₜₐₗ is to be positive

Question 33

If both △Sₛᵧₛ and △Hₛᵧₛ are negative what temp is more likely to be feasible

Answer 33

more likely to be feasible as temp decreases, so △Sₛᵧₛ > △Hₛᵧₛ/temp