Entropy + Gibbs Free Energy

Question 1

Definition of feasible?

What factors determine whether a reaction is feasible? (3)

Answer 1

How likely a reaction is going is going to occur

• Temperature
• Enthalpy
• Entropy

Question 2

What is entropy?
Units?

Answer 2

The amount of ‘disorder’ within a system

JK-1mol-1

Question 3

Which has more entropy?

• Solid or Aqueous
• Aqueous or Gas

Answer 3

Aqueous
Gas

Question 4

Has the entropy increased or decreased? Why?

Mg(s) + 2HCl(aq) ——> MgCl2(aq) + H2(g)

Answer 4

Increased - Gas is made

Question 5

Has the entropy increased or decreased? Why?

C2H6(g) + 3.5O2(g) ——> 2CO2(g) + 3H2O(g)

Answer 5

Increased - More particles on products as 4.5:5 + they’re all the same state

Question 6

Equation to calculating change in entropy (△S)?

Answer 6

△S = ∑S (products) - ∑S (reactants)

Question 7

Equation for Gibbs free energy change (△G)? Units?

Answer 7

Question 8

What does the Gibbs free energy show?

Answer 8

Whether the reaction is feasible by △G⪬0

Question 9

Why might a chemical reaction be feasible according to thermodynamics but not in real life?

Answer 9

Kinetic factors may prevent a reaction from occurring like having high Ea so few particles have energy to react/to react at slow rate

Question 10

Suggest why the enthalpy change for the thermal decomposition of solid AgNO2 is difficult to determine experimentally?

Answer 10

AgNO2 has to be heated so can’t measure the temperature change caused by reaction

Question 11

Answer 11