Multiple Choice
What is the equilibrium constant, Kp, for the reaction MgCO3(s) ⇌ MgO(s) + CO2(g) at 25 °C given that ΔG° = 48.2 kJ?
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16. Chemical Equilibrium
Equilibrium Constant K
Multiple Choice
Which of the following is the correct equilibrium constant expression for the reaction: 3H+(aq) + PO4^3-(aq) ⇌ H3PO4(aq)?
A
K = [H+]^3[PO4^3-] / [H3PO4]
B
K = [H3PO4] / ([H+]^3[PO4^3-])
C
K = [H3PO4] / [H+][PO4^3-]
D
K = [H+]^3 / ([H3PO4][PO4^3-])
Verified step by step guidance1
Identify the general form of the equilibrium constant expression for a reaction: For a reaction aA + bB ⇌ cC + dD, the equilibrium constant expression is K = ([C]^c[D]^d) / ([A]^a[B]^b).
Apply the general form to the given reaction: 3H+(aq) + PO4^3-(aq) ⇌ H3PO4(aq). Here, the reactants are H+ and PO4^3-, and the product is H3PO4.
Write the equilibrium constant expression: The expression will be K = [H3PO4] / ([H+]^3[PO4^3-]), where [H3PO4] is the concentration of the product, and [H+]^3 and [PO4^3-] are the concentrations of the reactants raised to the power of their stoichiometric coefficients.
Compare the given options with the derived expression: The correct expression is K = [H3PO4] / ([H+]^3[PO4^3-]), which matches one of the provided options.
Understand why the other options are incorrect: The other options either do not correctly represent the stoichiometric coefficients or incorrectly place reactants/products in the numerator/denominator of the expression.
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