Calculate Delta G for The Following Reaction 21co2

What is ΔG?

The Gibbs free energy change (ΔG) is a thermodynamic property that measures the energy available to do work in a chemical reaction. It combines enthalpy (ΔH) and entropy (ΔS) according to the equation:

Where:

• ΔG = Gibbs free energy change (kJ/mol)
• ΔH = Enthalpy change (kJ/mol)
• T = Absolute temperature (K)
• ΔS = Entropy change (J/mol·K)

ΔG is particularly important because it determines whether a reaction is spontaneous (ΔG < 0) or non-spontaneous (ΔG > 0).

How to calculate ΔG

To calculate ΔG for a reaction, you need:

1. The standard Gibbs free energy of formation (ΔG°f) for all reactants and products
2. The stoichiometric coefficients of the balanced chemical equation
3. The temperature at which the reaction occurs

The calculation follows this formula:

For temperature dependence, use the standard Gibbs free energy change at 298 K (ΔG°298) and adjust for temperature using:

Where Q is the reaction quotient.

Standard conditions

Standard conditions for Gibbs free energy calculations are:

• Temperature: 298 K (25°C)
• Pressure: 1 atm (101.325 kPa)
• Concentration: 1 M for solutes
• Pure solids and liquids at 1 atm pressure

Standard Gibbs free energy values (ΔG°f) are typically reported under these conditions.

Reaction spontaneity

The sign of ΔG determines reaction spontaneity:

• ΔG < 0: Spontaneous reaction (energy is released)
• ΔG = 0: Equilibrium (no net change)
• ΔG > 0: Non-spontaneous reaction (energy must be added)

For the reaction 2CO2 + O2 → 2CO2 + ΔG, the ΔG value indicates whether the reaction will proceed under standard conditions.

Example calculation

Let's calculate ΔG for the hypothetical reaction:

2CO2 + O2 → 2CO2 + ΔG

Assuming standard Gibbs free energy values:

• ΔG°f(CO2) = -394.4 kJ/mol
• ΔG°f(O2) = 0 kJ/mol

The calculation would be:

This result shows the reaction is at equilibrium under standard conditions.