Chapter 22 - Enthalpy and Entropy

Question 1

What is the equation for change in entropy?

Answer 1

∆S = S(products) - S(reactants)

Question 2

What is the equation for Gibb’s free energy?

Answer 2

ΔG = ΔH - TΔS

Question 3

What is entropy?

Answer 3

A measure of the dispersal of energy in a system

Question 4

Magnitudes of entropy in (1) solids, (2) liquids, (3) gases:

Answer 4

1. Lowest
2. Highest

↑ in gas molecules ↑ entropy/disorder because they are free to move

Question 5

What does the feasibility of a reaction rely on?

Answer 5

• Entropy change
• Temperature of system
• Enthalpy change of system

ΔG = ΔH - TΔS

Question 6

• ΔG < 0
• ΔG = 0
• ΔG > 0

Answer 6

• Reaction is more feasible
• Reaction in equ. and feasible
• Reaction not feasible

Question 7

What are the limitations of using Gibb’s free energy to predict feasibility?

Answer 7

Many reactions with negative ΔG do not take place because of high activation energies therefore a very small rate.

(ΔG indicates feasibility but does not account for kinetics or rate)

Question 8

Define lattice enthalpy

Answer 8

Formation of 1 mol of an ionic lattice from gaseous ions

Question 9

Define enthalpy change of atomisation

Answer 9

Enthalpy change that takes place when 1
mol of gaseous atoms is formed from an element in its standard state

Question 10

Define enthalpy change of formation

Answer 10

Enthalpy change that takes place when 1 mol
of a compound is formed from its elements

Question 11

Define enthalpy change of hydration

Answer 11

The enthalpy change that takes place when 1 mol of gaseous ions are dissolved in water

Question 12

Define enthalpy change of solution

Answer 12

The enthalpy change that takes place when 1 mol of solute is dissolved

Question 13

What affects lattice enthalpy and enthalpy of hydration?

Answer 13

• ↑ ionic radius, ↑ enthalpies
• ↑ ionic charge, ↓ enthalpies

Question 14

If enthalpy of hydration is greater than lattice enthalpy, it means…

Answer 14

that the compound should dissolve