Topic 13 Entropy

Question 1

What is a spotnaneous process

Answer 1

One that takes place without continuous intervention from us, reverse will never happen on its own

Question 2

Define Entropy and what do systems tend towards

Answer 2

A quantity associated with randomness or disorder, always want higher entropy

Question 3

What total entropy change is there in spontaneous reaction

Answer 3

Positive

Question 4

How to calculate total entropy

Answer 4

Change in system + Change in surroundings

Question 5

How to caluculate entropy change of system

Answer 5

products - reactants

Question 6

Calculate entropy change of surroundings

Answer 6

Surroundings = minus Change in enthalpy / temperature (kelvin)

Question 7

How does temperature impact entropy

Answer 7

Increase in temperature at higher entropy has less positive effect than at lower entropy (temperature)

Question 8

Why may a reaction that is not thermodynamically feasible occur

Answer 8

Non standard conditions

Question 9

How to calculate Gibbs Free Energy

Answer 9

Change in enthalpy - T(entropy change system)

Question 10

What does different values for Gibbs Free Energy mean

Answer 10

positive - not feasible
negative - feasible
0 = equilibrium

Question 11

Equilibrium constant Gibbs Free energy equation

Answer 11

Gibbs = -RTlnK

Question 12

Why may a reaction that is thermodynamically not feasible occur

Answer 12

Higher activation than the temperature it is spontaneous at. Called kinetic stablility

Question 13

Experimental vs theoretical lattice energy

Answer 13

Experimental is calculated through Born Haber Cycle, theoretical is done using calculations

Question 14

Assumptions made with theoretical lattice energy

Answer 14

Ions are in contact with each other
Ions are perfectly spherical
Charge on each ion is evenly distributed around the centre so that each ion can be considered as point charges

Question 15

Why may experimental be higher than theoretical

Answer 15

Covalent properties of lattice structure due to polariation of anion

Question 16

Factors affecting polarisation of anion

Answer 16

High charge and small size of cation . charge density high

Question 17

Factors affecting polarising ability of cation

Answer 17

High charge and large size of anion. most easily polarised

Question 18

Lattice Energy, ΔlatticeHꝊ

Answer 18

The energy change when one mole of an ionic solid is formed from its gaseous ions under standard conditions

Provides a measure of ionic bond strength

Question 19

Enthalpy Change of Atomisation, ΔatHꝊ

Answer 19

The enthalpy change when one mole of gaseous atoms are formed from an element in its standard state.

Question 20

Electron Affinity, EeaꝊ

Answer 20

The energy change when one mole of electrons is gained by one mole of gaseous atoms or anions to form one mole of gaseous anions.

Question 21

Enthalpy change of solution, ΔsolHꝊ

Answer 21

The enthalpy change when one mole of an ionic solid dissolves in excess water to form an infinitely dilute solution.

Question 22

Enthalpy Change of hydration, ΔhydHꝊ

Answer 22

The enthalpy change when one mole of an ion in its gaseous state is
completely hydrated by water to form an infinitely dilute solution.

Question 23

Dissolving ammonium nitrate in water

Answer 23

Entropy change is positive
Endothermic Reaction
Solid to aqueous. 1 mol to 2 moles

Question 24

Ethanoic acid with ammonium carbonate

Answer 24

Bubbles of gas are violently produced
Endothermic
Entropy positive
gas is produced

Question 25

Magnesium ribbon burnt in air

Answer 25

Highly exothermic
entropy system negative but total positive
Doesn’t occur at room temp due to activation energy being too high