For a reaction involving only gases at 25?C the equilibrium constant can be expressed in terms of molarity Ke or partial pressure Kp. Which is true about the numerical value of Kp ?
Correct answer: D. Kc is equal to Kp if the total moles of reactants and products are equal
- A. Kc is generally greaer than Kp
- B. Kc is generally less than Kp
- C. Kc is generally equal to Kp
- D. Kc is equal to Kp if the total moles of reactants and products are equal
Explanation
The relationship is Kp = Kc(RT)^Δn, where Δn is the difference between gaseous product and reactant coefficients. If the total moles of gaseous reactants and products are equal, Δn = 0, so Kp = Kc. The common mistake is choosing that Kc is generally greater or less than Kp without checking Δn.
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About Le Chatelier's Principle
Le Chatelier's principle predicts how an equilibrium responds when concentration, pressure or temperature changes. Questions apply it to reversible reactions, identify the direction of shift and distinguish genuine equilibrium changes from the effect of a catalyst, which changes the rate of reaching equilibrium but not its position.
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