Question

2CrO₄²⁻(aq)+2H+(aq)⇌Cr₂O7 2−(aq)+H₂O(l)

Write the equation for the equilibrium constant (K) of the reaction studied in this exercise.

Answer 1

The equation for the equilibrium constant K for the given reaction is K = [Cr₂O₇²-] / ([CrO₄²-]²[H+]²). Water is often omitted from the equilibrium expression as its concentration remains constant.

Step-by-step explanation:

The student has asked how to write the equation for the equilibrium constant (K) for the reaction between chromate ions (CrO42-) and hydrogen ions (H+) to form dichromate ions (Cr2O72-) and water (H2O). The balanced chemical equation provided is 2CrO42-(aq) + 2H+(aq) ⇌ Cr2O72-(aq) + H2O(l). To write the equilibrium constant expression for this reaction, we take the concentration of the products raised to the power of their stoichiometric coefficients, divided by the concentration of the reactants raised to the power of their coefficients. The correct equilibrium expression is:

K = [Cr2O72-][H2O]1 / ([CrO42-]2[H+]2)

Since the concentration of water in a dilute aqueous solution is approximately constant, it is often omitted from the equilibrium expression, yielding:

K = [Cr2O72-] / ([CrO42-]2[H+]2)