Question detail
A reaction at equilibrium has a Kc value of 4.0 at a certain temperature. If the equilibrium concentrations of the reactants are [A] = 0.5 mol/dm³ and [B] = 0.5 mol/dm³, what is the equilibrium concentration of product C?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Chemical equilibria, Le Chatelier's principle and Kc
Question
- A. 1.0 mol/dm³
- B. 2.0 mol/dm³ (A-level cue 94bb87d3 distractor 1)
- C. 0.5 mol/dm³ (A-level cue 94bb87d3 distractor 2)
- D. 0.25 mol/dm³ (A-level cue 94bb87d3 distractor 3)
Answer
1.0 mol/dm³
Explanation
The correct option is 1.0 mol/dm³. 1.0 mol/dm³ is correct because it supports the objective: Calculate equilibrium concentrations from Kc where appropriate.. The reasoning stays within Equilibrium constant Kc and avoids drifting into a similar A-Level Chemistry idea. This item is treated as conceptual revision rather than a formal calculation item because the validated answer is an explanation or option choice, not a worked numerical response.
Common mistake
Incorrect Calculation of Equilibrium Concentrations
Students often forget to use the correct Kc expression when calculating equilibrium concentrations, leading to incorrect values.
To fix this, remember to write the Kc expression based on the balanced equation. For example, for the reaction aA + bB ⇌ cC + dD, the Kc expression is Kc = [C]^c [D]^d / [A]^a [B]^b. Substitute the equilibrium concentrations into the expression and solve for the unknown concentration.
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