Gibbs Free Energy Spring 22

Front

What is Gibbs Free Energy (ΔG) and why is it important in thermodynamics?

Back

Gibbs Free Energy (ΔG) is a thermodynamic potential that measures the maximum reversible work obtainable from a thermodynamic system at constant temperature and pressure. It is important because it helps predict the spontaneity of a reaction; if ΔG is negative, the reaction is spontaneous.

Front

What are the signs of ΔH, ΔS, and ΔG for the reaction Mg(s) → Mg(g) at high temperature?

Back

ΔH = +, ΔS = +, ΔG = - (At high temperature). This indicates that the reaction is endothermic and increases disorder, leading to spontaneity at high temperatures.

Front

How do you calculate ΔG° using ΔH° and ΔS°?

Back

ΔG° = ΔH° - TΔS°, where T is the temperature in Kelvin. This equation allows you to determine the Gibbs Free Energy change under standard conditions.

Front

What does a high negative enthalpy (ΔH) indicate about a reaction?

Back

A high negative enthalpy (ΔH) indicates that the reaction releases a significant amount of heat, which favors spontaneity.

Front

What combination of ΔH and ΔS will NEVER lead to a spontaneous reaction?

Back

The combination of +ΔH and -ΔS will NEVER lead to a spontaneous reaction, as it indicates that the reaction is endothermic and decreases disorder.

Front

What is the significance of entropy (ΔS) in determining the spontaneity of a reaction?

Back

Entropy (ΔS) measures the disorder or randomness of a system. A positive ΔS indicates an increase in disorder, which favors spontaneity, especially at higher temperatures.

Front

What temperature conditions are required for a reaction with positive ΔH and positive ΔS to be spontaneous?

Back

For a reaction with positive ΔH and positive ΔS to be spontaneous, very high temperatures are required to overcome the positive enthalpy.

Front

What is the relationship between temperature and spontaneity in thermodynamic reactions?

Back

Temperature affects the spontaneity of reactions by influencing the balance between enthalpy (ΔH) and entropy (ΔS). Higher temperatures can make reactions with positive ΔS more likely to be spontaneous.

Front

What is the standard state of a substance in thermodynamics?

Back

The standard state of a substance is its most stable form at 1 bar (or 1 atm) of pressure and a specified temperature, usually 25°C (298 K). This is used as a reference point for thermodynamic calculations.

Front

How does the sign of ΔG relate to the equilibrium of a reaction?

Back

If ΔG is negative, the reaction is spontaneous and will proceed in the forward direction. If ΔG is positive, the reaction is non-spontaneous and will favor the reverse direction. If ΔG = 0, the system is at equilibrium.