Question 1

Identify the compound with the highest standard free energy of formation.

Accepted Answer

The standard free energy of formation ($ \Delta G_f^{\circ} $) is a measure of the energy change when 1 mole of a compound is formed from its elements in their standard states. Among the given options, ozone (O3), represented here as O₃(g), is known to have a relatively high standard free energy of formation due to its unstable and reactive nature compared to the other compounds listed, which are more stable.

Question 2

Determine ΔG°_rxn for the following reaction at 338 K. FeO(s)+ CO(g)→ Fe(s)+ CO₂(g)ΔH°= -11.0 kJ; ΔS°= -17.4 J/K

Accepted Answer

To calculate ΔG° for the reaction, use the formula ΔG° = ΔH° - TΔS°. Convert ΔS° to kJ by dividing by 1000 (since it's given in J/K), ΔS° = -17.4 J/K = -0.0174 kJ/K. Then, plug in the values: ΔG° = -11.0 kJ - (338 K)(-0.0174 kJ/K) = -11.0 kJ + 5.9 kJ = -5.1 kJ.

Question 3

Identify the compound with the standard free energy of formation equal to zero.

Accepted Answer

The standard free energy of formation is zero for elements in their standard states. H₂(g) is an element in its standard state.

Question 4

Given the following equation, C₃H₈(g)+ 5 O₂(g)→ 3 CO₂(g)+ 4 H₂O(g)ΔG°_rxn = -2074 kJ Calculate ΔG°_rxn for the following reaction. 21 CO₂(g)+ 28 H₂O(g)→ 7 C₃H₈(g)+ 35 O₂(g)

Accepted Answer

The given reaction is the reverse of the original reaction multiplied by 7. Reversing the reaction changes the sign of ΔG° and multiplying by 7 scales it by 7, resulting in +14518 kJ.

Question 5

Determine ΔG°_rxn for the following reaction at 358 K. CaCO₃(s)→ CaO(s)+ CO₂(g)ΔH°= +179.2 kJ; DS°= +160.2 J/K

Accepted Answer

ΔG° = ΔH° - TΔS°. Convert ΔS° to kJ (160.2 J/K = 0.1602 kJ/K). ΔG° = 179.2 kJ - (358 K * 0.1602 kJ/K) = 179.2 kJ - 57.4 kJ = 121.8 kJ.

Question 6

Calculate ΔS°_rxn for the following reaction.The S° for each species is shown below the reaction. 4 NH₃(g)+ 5 O₂(g)→ 4 NO(g)+ 6 H₂O(g) S°(J/mol∙K)192.8 205.2 210.8 188.8

Accepted Answer

The answer of Calculate ΔS°_rxn for the following reaction.The S°...

Question 7

Estimate ΔG°_rxn for the following reaction at 825 K. 2 Hg(g)+ O₂(g)→ 2 HgO(s)ΔH°= -304.2 kJ; ΔS°= -414.2 J/K

Accepted Answer

The answer of Estimate ΔG°_rxn for the following reaction at...

Question 8

Estimate ΔG°_rxn for the following reaction at 417 K. HCN(g)+ 2 H₂(g)→ CH₃NH₂(g)ΔH°= -158.0 kJ; ΔS°= -219.9 J/K

Accepted Answer

ΔG° = ΔH° - TΔS°. Substituting the given values: ΔG° = -158.0 kJ - (417 K)(-219.9 J/K × 1 kJ/1000 J) = -158.0 kJ + 91.6 kJ = -66.3 kJ.

Question 9

Which one of the following would be expected to have the lowest standard molar entropy,S°,at 25°C?

Accepted Answer

Entropy is a measure of the disorder or randomness of a system. Solids have the lowest entropy because their particles are fixed in place, compared to liquids and gases where particles have more freedom of movement. Therefore, the solid state (A) would have the lowest standard molar entropy at 25°C.

Question 10

Given the following equation, H₂O(g)+ CO(g)→ H₂(g)+ CO₂(g)ΔG°_rxn = -28.6 kJ Calculate ΔG°_rxn for the following reaction. 5 H₂(g)+ 5 CO₂(g)→ 5 H₂O(g)+ 5 CO(g)

Accepted Answer

The given reaction is the reverse of the original reaction and is multiplied by 5. Therefore, ΔG° for the reverse reaction is +28.6 kJ, and when multiplied by 5, it becomes +143.0 kJ.

Question 11

Calculate ΔS°_rxn for the following reaction.The S^∘for each species is shown below the reaction. C₂H₂(g)+ 2 H₂(g)→ C₂H₆(g) S°(J/mol∙K)200.9 130.7 229.2

Accepted Answer

ΔS°_rxn = ∑[S°(products)] - ∑[S°(reactants)] = [2(130.7 J/mol∙K) + 229.2 J/mol∙K] - [200.9 J/mol∙K + 2(130.7 J/mol∙K)] = 233.1 J/K Note that the coefficients in the balanced equation do not affect the ΔS° value, so we do not need to multiply any of the S° values by the coefficients. Therefore, the correct answer is D, -233.1 J/K.

Question 12

Estimate ΔG°_rxn for the following reaction at 449.0 K. CH₂O(g)+ 2 H₂(g)→ CH₄(g)+ H₂O(g)ΔH°= -94.9 kJ; ΔS°= -224.2 J/K

Accepted Answer

The correct answer is calculated using the Gibbs free energy equation: ΔG° = ΔH° - TΔS°. Plugging in the given values (ΔH° = -94.9 kJ and ΔS° = -224.2 J/K, with T = 449.0 K), and converting ΔS° to kJ (by dividing by 1000), we get ΔG° = -94.9 kJ - (449.0 K)(-224.2 J/K / 1000) = -94.9 kJ + 100.6 kJ = +5.8 kJ.

Question 13

Given the following equation, N₂O(g)+ NO₂(g)→ 3 NO(g)ΔG°_rxn = -23.0 kJ Calculate ΔG°_rxn for the following reaction. 6 N₂O(g)+ 6 NO₂(g)→ 18 NO(g)

Accepted Answer

Since the coefficients of the given equation are multiplied by 6 in the new equation, ΔG°_rxn must also be multiplied by 6. Thus, ΔG°_rxn = -23.0 kJ x 6 = -138 kJ. Therefore, the answer is C, -138 kJ.

Question 14

Calculate ΔS°_rxn for the following reaction.The S° for each species is shown below the reaction. N₂H₄(l)+ H₂(g)→ 2 NH₃(g) S° (J/mol∙K)121.2 130.7 192.8

Accepted Answer

The correct answer is A because the change in entropy is calculated by subtracting the sum of the entropies of the reactants from the sum of the entropies of the products. In this case, the change in entropy is 192.8 J/mol∙K + 130.7 J/mol∙K - 121.2 J/mol∙K = 202.3 J/mol∙K.

Question 15

Identify the compound with the most negative standard free energy of formation.

Accepted Answer

NaF(s) has a highly negative standard free energy of formation because it is a stable ionic compound formed from the reaction of a highly reactive alkali metal, sodium (Na), with a highly reactive halogen, fluorine (F). This results in the release of a large amount of energy, making its formation highly favorable energetically.

Question 16

Given the following equation, H₂O(g)+ CO(g)→ H₂(g)+ CO₂(g)ΔG°_rxn = -28.6 kJ Calculate ΔG°_rxn for the following reaction. 8 H₂O(g)+ 8 CO(g)→ 8 H₂(g)+ 8 CO₂(g)

Accepted Answer

ΔG°_rxn for the given equation is -28.6 kJ. Now, for the given reaction, we have 8 times the balanced equation of the given equation. Hence, the ΔG°_rxn for the given reaction will be: ΔG°_rxn = 8(-28.6 kJ) = -228.8 kJ Therefore, the best choice is A, which is the calculated value of ΔG°_rxn for the given reaction.

Question 17

Given the following equation, N₂O(g)+ NO₂(g)→ 3 NO(g)ΔG°_rxn = -23.0 kJ Calculate ΔG°_rxn for the following reaction. 18 NO(g)→ 6 N₂O(g)+ 6 NO₂(g)

Accepted Answer

The given reaction is the reverse of the original reaction multiplied by 6. Therefore, ΔG° for the reverse reaction is +23.0 kJ, and multiplying by 6 gives 138 kJ.

Question 18

Calculate DS°_rxn for the following reaction.The S° for each species is shown below the reaction. P₄(g)+ 10 Cl₂(g)→ 4 PCl₅(g) S°(J/mol∙K)280.0 223.1 364.6

Accepted Answer

The answer of Calculate DS°_rxn for the following reaction.The S°...

Question 19

Identify the compound that is an allotrope of carbon.

Accepted Answer

Graphite is a well-known allotrope of carbon, which means it is a different form of the same element. Methanol, baking soda, gasoline, and sugar are not allotropes of carbon.

Question 20

Given the following equation, C₃H₈(g)+ 5 O₂(g)→ 3 CO₂(g)+ 4 H₂O(g)ΔG°_rxn = -2074 kJ Calculate ΔG°_rxn for the following reaction. 7 C₃H₈(g)+ 35 O₂(g)→ 21 CO₂(g)+ 28 H₂O(g)

Accepted Answer

The given equation is the same as the given reaction but scaled up by a factor of 5. This means that the ΔG°_rxn value for the given reaction is also scaled up by a factor of 5: ΔG°_rxn = (-2074 kJ) * 5 = -10370 kJ Therefore, the correct choice is C (-14518 kJ is the opposite sign of the correct answer and the other choices are not even close to the correct answer).

Quiz 18: Free Energy and Thermodynamics

Identify the compound with the highest standard free energy of formation.

Determine ΔG°_rxn for the following reaction at 338 K. FeO(s) + CO(g) → Fe(s) + CO₂(g) ΔH°= -11.0 kJ; ΔS°= -17.4 J/K

Identify the compound with the standard free energy of formation equal to zero.

Given the following equation, C₃H₈(g) + 5 O₂(g) → 3 CO₂(g) + 4 H₂O(g) ΔG°_rxn = -2074 kJ Calculate ΔG°_rxn for the following reaction. 21 CO₂(g) + 28 H₂O(g) → 7 C₃H₈(g) + 35 O₂(g)

Determine ΔG°_rxn for the following reaction at 358 K. CaCO₃(s) → CaO(s) + CO₂(g) ΔH°= +179.2 kJ; DS°= +160.2 J/K

Calculate ΔS°_rxn for the following reaction.The S° for each species is shown below the reaction. 4 NH₃(g) + 5 O₂(g) → 4 NO(g) + 6 H₂O(g) S°(J/mol∙K) 192.8 205.2 210.8 188.8

Estimate ΔG°_rxn for the following reaction at 825 K. 2 Hg(g) + O₂(g) → 2 HgO(s) ΔH°= -304.2 kJ; ΔS°= -414.2 J/K

Estimate ΔG°_rxn for the following reaction at 417 K. HCN(g) + 2 H₂(g) → CH₃NH₂(g) ΔH°= -158.0 kJ; ΔS°= -219.9 J/K

Which one of the following would be expected to have the lowest standard molar entropy,S°,at 25°C?

Given the following equation, H₂O(g) + CO(g) → H₂(g) + CO₂(g) ΔG°_rxn = -28.6 kJ Calculate ΔG°_rxn for the following reaction. 5 H₂(g) + 5 CO₂(g) → 5 H₂O(g) + 5 CO(g)

Calculate ΔS°_rxn for the following reaction.The S^∘for each species is shown below the reaction. C₂H₂(g) + 2 H₂(g) → C₂H₆(g) S°(J/mol∙K) 200.9 130.7 229.2

Estimate ΔG°_rxn for the following reaction at 449.0 K. CH₂O(g) + 2 H₂(g) → CH₄(g) + H₂O(g) ΔH°= -94.9 kJ; ΔS°= -224.2 J/K

Given the following equation, N₂O(g) + NO₂(g) → 3 NO(g) ΔG°_rxn = -23.0 kJ Calculate ΔG°_rxn for the following reaction. 6 N₂O(g) + 6 NO₂(g) → 18 NO(g)

Calculate ΔS°_rxn for the following reaction.The S° for each species is shown below the reaction. N₂H₄(l) + H₂(g) → 2 NH₃(g) S° (J/mol∙K) 121.2 130.7 192.8

Identify the compound with the most negative standard free energy of formation.

Given the following equation, H₂O(g) + CO(g) → H₂(g) + CO₂(g) ΔG°_rxn = -28.6 kJ Calculate ΔG°_rxn for the following reaction. 8 H₂O(g) + 8 CO(g) → 8 H₂(g) + 8 CO₂(g)

Given the following equation, N₂O(g) + NO₂(g) → 3 NO(g) ΔG°_rxn = -23.0 kJ Calculate ΔG°_rxn for the following reaction. 18 NO(g) → 6 N₂O(g) + 6 NO₂(g)

Calculate DS°_rxn for the following reaction.The S° for each species is shown below the reaction. P₄(g) + 10 Cl₂(g) → 4 PCl₅(g) S°(J/mol∙K) 280.0 223.1 364.6

Identify the compound that is an allotrope of carbon.

Given the following equation, C₃H₈(g) + 5 O₂(g) → 3 CO₂(g) + 4 H₂O(g) ΔG°_rxn = -2074 kJ Calculate ΔG°_rxn for the following reaction. 7 C₃H₈(g) + 35 O₂(g) → 21 CO₂(g) + 28 H₂O(g)

Quiz 18: Free Energy and Thermodynamics

Identify the compound with the highest standard free energy of formation.

Determine ΔG°rxn for the following reaction at 338 K. FeO(s) + CO(g) → Fe(s) + CO2(g) ΔH°= -11.0 kJ; ΔS°= -17.4 J/K

Identify the compound with the standard free energy of formation equal to zero.

Given the following equation, C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g) ΔG°rxn = -2074 kJ Calculate ΔG°rxn for the following reaction. 21 CO2(g) + 28 H2O(g) → 7 C3H8(g) + 35 O2(g)

Determine ΔG°rxn for the following reaction at 358 K. CaCO3(s) → CaO(s) + CO2(g) ΔH°= +179.2 kJ; DS°= +160.2 J/K

Calculate ΔS°rxn for the following reaction.The S° for each species is shown below the reaction. 4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2O(g) S°(J/mol∙K) 192.8 205.2 210.8 188.8

Estimate ΔG°rxn for the following reaction at 825 K. 2 Hg(g) + O2(g) → 2 HgO(s) ΔH°= -304.2 kJ; ΔS°= -414.2 J/K

Estimate ΔG°rxn for the following reaction at 417 K. HCN(g) + 2 H2(g) → CH3NH2(g) ΔH°= -158.0 kJ; ΔS°= -219.9 J/K

Which one of the following would be expected to have the lowest standard molar entropy,S°,at 25°C?

Given the following equation, H2O(g) + CO(g) → H2(g) + CO2(g) ΔG°rxn = -28.6 kJ Calculate ΔG°rxn for the following reaction. 5 H2(g) + 5 CO2(g) → 5 H2O(g) + 5 CO(g)

Calculate ΔS°rxn for the following reaction.The S∘ for each species is shown below the reaction. C2H2(g) + 2 H2(g) → C2H6(g) S°(J/mol∙K) 200.9 130.7 229.2

Estimate ΔG°rxn for the following reaction at 449.0 K. CH2O(g) + 2 H2(g) → CH4(g) + H2O(g) ΔH°= -94.9 kJ; ΔS°= -224.2 J/K

Given the following equation, N2O(g) + NO2(g) → 3 NO(g) ΔG°rxn = -23.0 kJ Calculate ΔG°rxn for the following reaction. 6 N2O(g) + 6 NO2(g) → 18 NO(g)

Calculate ΔS°rxn for the following reaction.The S° for each species is shown below the reaction. N2H4(l) + H2(g) → 2 NH3(g) S° (J/mol∙K) 121.2 130.7 192.8

Identify the compound with the most negative standard free energy of formation.

Given the following equation, H2O(g) + CO(g) → H2(g) + CO2(g) ΔG°rxn = -28.6 kJ Calculate ΔG°rxn for the following reaction. 8 H2O(g) + 8 CO(g) → 8 H2(g) + 8 CO2(g)

Given the following equation, N2O(g) + NO2(g) → 3 NO(g) ΔG°rxn = -23.0 kJ Calculate ΔG°rxn for the following reaction. 18 NO(g) → 6 N2O(g) + 6 NO2(g)

Calculate DS°rxn for the following reaction.The S° for each species is shown below the reaction. P4(g) + 10 Cl2(g) → 4 PCl5(g) S°(J/mol∙K) 280.0 223.1 364.6

Identify the compound that is an allotrope of carbon.

Given the following equation, C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g) ΔG°rxn = -2074 kJ Calculate ΔG°rxn for the following reaction. 7 C3H8(g) + 35 O2(g) → 21 CO2(g) + 28 H2O(g)

Determine ΔG°_rxn for the following reaction at 338 K. FeO(s) + CO(g) → Fe(s) + CO₂(g) ΔH°= -11.0 kJ; ΔS°= -17.4 J/K

Given the following equation, C₃H₈(g) + 5 O₂(g) → 3 CO₂(g) + 4 H₂O(g) ΔG°_rxn = -2074 kJ Calculate ΔG°_rxn for the following reaction. 21 CO₂(g) + 28 H₂O(g) → 7 C₃H₈(g) + 35 O₂(g)

Determine ΔG°_rxn for the following reaction at 358 K. CaCO₃(s) → CaO(s) + CO₂(g) ΔH°= +179.2 kJ; DS°= +160.2 J/K

Calculate ΔS°_rxn for the following reaction.The S° for each species is shown below the reaction. 4 NH₃(g) + 5 O₂(g) → 4 NO(g) + 6 H₂O(g) S°(J/mol∙K) 192.8 205.2 210.8 188.8

Estimate ΔG°_rxn for the following reaction at 825 K. 2 Hg(g) + O₂(g) → 2 HgO(s) ΔH°= -304.2 kJ; ΔS°= -414.2 J/K

Estimate ΔG°_rxn for the following reaction at 417 K. HCN(g) + 2 H₂(g) → CH₃NH₂(g) ΔH°= -158.0 kJ; ΔS°= -219.9 J/K

Given the following equation, H₂O(g) + CO(g) → H₂(g) + CO₂(g) ΔG°_rxn = -28.6 kJ Calculate ΔG°_rxn for the following reaction. 5 H₂(g) + 5 CO₂(g) → 5 H₂O(g) + 5 CO(g)

Calculate ΔS°_rxn for the following reaction.The S^∘for each species is shown below the reaction. C₂H₂(g) + 2 H₂(g) → C₂H₆(g) S°(J/mol∙K) 200.9 130.7 229.2

Estimate ΔG°_rxn for the following reaction at 449.0 K. CH₂O(g) + 2 H₂(g) → CH₄(g) + H₂O(g) ΔH°= -94.9 kJ; ΔS°= -224.2 J/K

Given the following equation, N₂O(g) + NO₂(g) → 3 NO(g) ΔG°_rxn = -23.0 kJ Calculate ΔG°_rxn for the following reaction. 6 N₂O(g) + 6 NO₂(g) → 18 NO(g)

Calculate ΔS°_rxn for the following reaction.The S° for each species is shown below the reaction. N₂H₄(l) + H₂(g) → 2 NH₃(g) S° (J/mol∙K) 121.2 130.7 192.8

Given the following equation, H₂O(g) + CO(g) → H₂(g) + CO₂(g) ΔG°_rxn = -28.6 kJ Calculate ΔG°_rxn for the following reaction. 8 H₂O(g) + 8 CO(g) → 8 H₂(g) + 8 CO₂(g)

Given the following equation, N₂O(g) + NO₂(g) → 3 NO(g) ΔG°_rxn = -23.0 kJ Calculate ΔG°_rxn for the following reaction. 18 NO(g) → 6 N₂O(g) + 6 NO₂(g)

Calculate DS°_rxn for the following reaction.The S° for each species is shown below the reaction. P₄(g) + 10 Cl₂(g) → 4 PCl₅(g) S°(J/mol∙K) 280.0 223.1 364.6

Given the following equation, C₃H₈(g) + 5 O₂(g) → 3 CO₂(g) + 4 H₂O(g) ΔG°_rxn = -2074 kJ Calculate ΔG°_rxn for the following reaction. 7 C₃H₈(g) + 35 O₂(g) → 21 CO₂(g) + 28 H₂O(g)