Gibbs Free Energy Calculations

Which equation correctly represents the free energy change in a chemical reaction?

• ΔG = ΔH + TΔS

• ΔG = ΔH - TΔS

• ΔG = ΔT - ΔHΔS

• ΔG = ΔS - TΔH

Given the following information, calculate ΔG⁰ for the reaction below at 25⁰C:

SnCl₄(l) + 2 H₂0(l) → SnO₂(S) + 4HCl(g),

ΔH⁰=133.0 kJ and ΔS⁰ =401.5 J/K

• -252.6 kJ

• -13.4 kJ

• 13.4 kJ

• 252.6 kJ

If a process is exothermic and not spontaneous, then what MUST be true?

• ΔS > 0

• ΔH > 0

• ΔG = 0

• ΔS < 0

In which of the following reactions/phase changes do you expect to have a decrease in entropy?

• Fe(s) →Fe(l)

• H₂O₂(l) →2H₂O(l) +O₂(g)

• 4Fe(s) +3O₂(g)→2Fe₂O₃(s)

• HF(l) →HF(g)

If ΔH and ΔS are both negative or positive, then ΔG has a -------------------sign.

• Positive

• Negative

• Variable

What is the change in enthalpy when ∆G =

‐114 kJ, ∆S = 188 J/K and T = 700 K?

• + 131.6 kJ

• -131.6 kJ

• +17.6 kJ

• -17.6 kJ

What is the value of ∆H if ∆G =

‐32.0 kJ, ∆S = +25.0 J/K and T = 20 C? Is this reaction spontaneous?

• 31.5 kJ, not spontaneous

• -32.5 kJ, spontaneous

• -24.7 kJ, spontaneous

• 39.3 kJ, not spontaneous

Tags

NGSS.HS-PS3-1

What is the temperature when ∆G = -12.2 kJ, ∆H = +12.0 kJ, ∆S = ‐52.0 J/K and T = 290 K?

• 237 K

• 467 K

• 523 K

• 383 K

The change of reactants into products will always be spontaneous if the products, compared to the reactants, have

• lower enthalpy and lower entropy

• lower enthalpy and higher entropy

• higher enthalpy and lower entropy

• higher enthalpy and higher entropy

Which tendencies favor a spontaneous reaction?

• decreasing enthalpy and decreasing entropy

• decreasing enthalpy and increasing entropy

• increasing enthalpy and decreasing entropy

• increasing enthalpy and increasing entropy