Understanding Free Energy Changes in Chemical Reactions

The video tutorial explains how to calculate the standard change in free energy (delta G naught) for the synthesis of ammonia from nitrogen and hydrogen gases. It demonstrates calculations at two different temperatures, 298 Kelvin and 1000 Kelvin, showing how temperature affects the thermodynamic favorability of the reaction. The tutorial also identifies a crossover temperature where the reaction shifts from being favorable to unfavorable, highlighting the balance between enthalpy and entropy.

What does a negative ΔG° indicate about a chemical reaction?

• The reaction is kinetically controlled.

• The reaction is endothermic.

• The reaction is thermodynamically favorable.

• The reaction is at equilibrium.

Which equation is used to calculate ΔG°?

• ΔG° = TΔS° - ΔH°

• ΔG° = ΔH° / TΔS°

• ΔG° = ΔH° + TΔS°

• ΔG° = ΔH° - TΔS°

Why is it necessary to convert ΔS° from joules to kilojoules?

• To match the units of ΔH°.

• To simplify the calculation.

• To increase the accuracy of the result.

• To make the equation dimensionless.

What is the value of ΔG° for the reaction at 298 K?

• Negative 106.5 kJ/mol

• Positive 106.5 kJ/mol

• Negative 33.0 kJ/mol

• Positive 33.0 kJ/mol

What does the superscript 'naught' (°) signify in ΔG°?

• The reaction is at standard conditions.

• The reaction is at non-standard conditions.

• The reaction is at equilibrium.

• The reaction is kinetically controlled.

At 1000 K, what is the sign of ΔG° for the ammonia synthesis reaction?

• Zero

• Positive

• Negative

• Undefined

What happens to the forward reaction at 1000 K?

• It becomes kinetically controlled.

• It becomes thermodynamically unfavorable.

• It remains at equilibrium.

• It becomes thermodynamically favorable.

What is the crossover temperature where ΔG° equals zero?

• 298 K

• 464 K

• 1000 K

• 273 K

At temperatures below the crossover point, what is the nature of the forward reaction?

• Thermodynamically unfavorable

• Kinetically controlled

• Thermodynamically favorable

• At equilibrium

What is the relationship between ΔH° and ΔS° at the crossover temperature?

• ΔH° is independent of TΔS°

• ΔH° is greater than TΔS°

• ΔH° is less than TΔS°

• ΔH° equals TΔS°