Math Problem Statement

Consider the reaction A + B ↔ C + D. After reaching equilibrium at 25°C, the following concentrations of reactants and products were measured: [A] = 10 µM, [B] = 15 µM, [C] = 10 µM, [D] = 10 µM. Calculate ΔG° for this reaction.

Solution

To calculate the standard Gibbs free energy change (ΔG\Delta G^\circ) for the given reaction at equilibrium, we can use the following formula derived from thermodynamics:

ΔG=RTlnKeq\Delta G^\circ = -RT \ln K_{\text{eq}}

Where:

  • RR is the universal gas constant (8.314J/mol\cdotpK8.314 \, \text{J/mol·K})
  • TT is the temperature in Kelvin. At 25°C, this is 298.15K298.15 \, \text{K}.
  • KeqK_{\text{eq}} is the equilibrium constant for the reaction, which can be calculated using the equilibrium concentrations of the reactants and products.

For the reaction A+BC+DA + B \rightleftharpoons C + D, the equilibrium constant KeqK_{\text{eq}} is expressed as:

[ K_{\text{eq}} = \frac{[C][D]}{[A][B]} ]

From the dataTo calculate the standard Gibbs free energy change (ΔG\Delta G^\circ) for the given reaction at equilibrium, we can use the following formula derived from thermodynamics:

ΔG=RTlnKeq\Delta G^\circ = -RT \ln K_{\text{eq}}

Where:

  • RR is the universal gas constant (8.314J/mol\cdotpK8.314 \, \text{J/mol·K})
  • TT is the temperature in Kelvin. At 25°C, this is 298.15K298.15 \, \text{K}.
  • KeqK_{\text{eq}} is the equilibrium constant for the reaction, which can be calculated using the equilibrium concentrations of the reactants and products.

For the reaction A+BC+DA + B \rightleftharpoons C + D, the equilibrium constant KeqK_{\text{eq}} is expressed as:

[ K_{\text{eq}} = \frac{[C][D]}{[A][B]} ]

From the

  • [A]=10μM=10×106M[A] = 10 \, \mu M = 10 \times 10^{-6} \, M
  • [B]=15μM=15×106M[B] = 15 \, \mu M = 15 \times 10^{-6} \, M
  • [C]=10μM=10×106M[C] = 10 \, \mu M = 10 \times 10^{-6} \, M
  • [D]=10μM=10×106M[D] = 10 \, \mu M = 10 \times 10^{-6} \, M

Let's first calculate KeqK_{\text{eq}} and then find ΔG\Delta G^\circ. I will now compute the results.The standard Gibbs free energy change (ΔG\Delta G^\circ) for the reaction is approximately 1005J/mol1005 \, \text{J/mol}, which matches the closest answer of 1000 J/mol.

Would you like further details or have any questions? Here are five related questions to expand on this topic:

  1. How does the equilibrium constant (KeqK_{\text{eq}}) influence the Gibbs free energy?
  2. What is the significance of a positive or negative ΔG\Delta G^\circ?
  3. How would a temperature change affect ΔG\Delta G^\circ for this reaction?
  4. Why is the Gibbs free energy important in determining the spontaneity of a reaction?
  5. How can you experimentally determine the equilibrium constant for a reaction?

Tip: Always remember to check if the reaction is at equilibrium before applying the formula for ΔG\Delta G^\circ, as it assumes equilibrium conditions.

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Math Problem Analysis

Mathematical Concepts

Thermodynamics
Equilibrium Chemistry

Formulas

ΔG° = -RT ln(K_eq)
K_eq = [C][D] / [A][B]

Theorems

Gibbs Free Energy Change
Equilibrium Constant

Suitable Grade Level

Grades 10-12