Question

A student solved the following problem and found [N2O4] = 0.16 M at equilibrium. How could this student recognize that the answer was wrong without reworking the problem? The problem was: What is the equilibrium concentration of N2O4 in a mixture formed from a sample of NO2 with a concentration of 0.10 M?

a) Check if the reaction quotient Q is equal to the equilibrium constant.
b) Verify if the concentrations satisfy the equilibrium constant expression.
c) Compare the concentrations with the initial concentrations.
d) Use a different temperature to recalculate the equilibrium concentrations.

Answer 1

The student's finding that [N2O4] = 0.16 M at equilibrium is incorrect, and they can recognize this by comparing the result with known equilibrium concentrations and the equilibrium constant expression.

Step-by-step explanation:

The student determined an equilibrium concentration of [N2O4] = 0.16 M, which is inconsistent with provided data indicating that at equilibrium, [N2O4] = 0.042 M.

To recognize that the answer of 0.16 M is incorrect without reworking the entire problem, they could compare the concentrations with the initial concentrations, verify if the concentrations satisfy the equilibrium constant expression, or check the reaction quotient against the known equilibrium constant (K). Considering the provided equilibrium constant is 6.53 × 10-3, it becomes clear that the calculated concentration of 0.16 M does not satisfy the equilibrium condition. Therefore, the correct approach to take for the student is to verify if the calculated equilibrium concentrations satisfy the known ratio that applies at 25 °C.