Unit 4: Chemical Systems & Equilibria

Question 0

Entropy is…..

Answer 0

A measure of the chaos, randomness, or disorder of a system

Question 1

When is a reaction considered spontaneous?

Answer 1

If it occurs when all you do is mix the reactants together

Question 2

What does the second law of thermodynamics state….?

Answer 2

Entropy is constantly increasing in the universe

Meaning the entropy change in the system & surroundings is always equal to the entropy change in the universe

Question 3

What are two ways entropy can be increased….?

Answer 3

Increase the amount of particles present
Make particles with more disorganized states
Solids = most organized
Gases = are most random

Question 4

Why do reactions favour the exothermic direction….?

Answer 4

It creates a system with lower energy making it more stable

Question 5

Why do reactions favour the direction that increases entropy….?

Answer 5

Follows second law of thermodynamics

The more negative deltaG is the more spontaneous the reaction

Question 6

If deltaH is negative and deltaS is positive, deltaG will be…..

Answer 6

Always negative
Forward rxn is favoured and it is spontaneous at any temp
Reverse rxn does not occur

Question 7

If deltaH is positive and deltaS is negative, deltaG is always…

Answer 7

Positive
Fwd rxn does not occur
Reverse rxn is favoured at any temp

Question 8

If deltaH is negative and DeltaS is negative, deltaG is…

Answer 8

Negative if T is small

Fwd is favoured at lower temp

Question 9

If both deltaH and DeltaS are positive, deltaG is…..?

Answer 9

Negative if T is large

Fwd favoured at high temp

Question 10

If deltaG is 0…

Answer 10

If factors are balanced fwd & rvs reaction can both be equally favoured

Question 11

Describe equilibrium

Answer 11

Fwd & rvs rxn occur simultaneously at the same speed so the amounts of products and reactants stay constant over time

Question 12

What 3 conditions are required in order for a system to be considered at equilibrium?

Answer 12

1. Dynamic change at the molecular level but no change at the macroscopic level meaning although reactants change to products and back there isn’t a physical change seen like colour, pressure, concentration or pH
2. Only achieved in a closed system meaning energy cannot be created or lost (constant temp needed)
3. Equilibrium can be approached from either direction you can start with all products or all reactants
4. Can be approached from either direction meaning you can start with all reactants or products and reach the same final concentrations