Chemistry Year 12 - Module 5 - Lesson 12

Reaction Quotient Q — Predicting Direction of Shift

Use this worksheet after reading the lesson to practise the key ideas and prove you can meet the success criteria.

Name
Date
Class

1. Key Ideas

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  • The definition of reaction quotient Q and how it differs from Keq
  • Why Q is a snapshot of current concentrations while Keq describes the equilibrium destination

2. Success Criteria

By the end, you should be able to:

  • The definition of reaction quotient Q and how it differs from Keq
  • The Q vs Keq decision rule: Q > Keq shifts left, Q < Keq shifts right, Q = Keq means no net change
  • How to calculate Q using the same algebraic expression as Keq but with current concentrations

3. Key Terms

Dynamic equilibriumA state where forward and reverse reaction rates are equal.
Le Chatelier's PrincipleA system at equilibrium shifts to minimise applied disturbances.
Equilibrium constant (Keq)The ratio of product to reactant concentrations at equilibrium.
Reaction quotient (Q)The ratio of product to reactant concentrations at any instant.
Closed systemA system where neither matter nor energy can escape to surroundings.
Reversible reactionA reaction that can proceed in both forward and reverse directions.

4. Activity: Build the Lesson Map

Use the lesson to complete the table. Keep answers brief but specific.

PromptYour answer
Main concept
Important example
Common mistake to avoid
How this links to the next lesson

5. Short Answer Questions

1. Explain this lesson goal in your own words: "The definition of reaction quotient Q and how it differs from Keq". Use one specific example from the lesson.

Band 32 marks

2. Apply this idea to a new example: "The Q vs Keq decision rule: Q > Keq shifts left, Q < Keq shifts right, Q = Keq means no net change". Show your reasoning clearly.

Band 43 marks

3. Analyse why this idea matters for understanding Reaction Quotient Q — Predicting Direction of Shift: "How to calculate Q using the same algebraic expression as Keq but with current concentrations".

Band 54 marks

6. Extend: Apply the Idea

Band 5/65 marks

A student gives a memorised answer about Reaction Quotient Q — Predicting Direction of Shift but does not use evidence or reasoning.

Improve the answer by writing a stronger response that uses accurate terminology, a relevant example and a clear explanation.

7. Multiple Choice

1. What is the best first step when answering a question about Reaction Quotient Q — Predicting Direction of Shift?

A. Identify the key concept being tested

B. Write every fact from memory

C. Ignore the command word

D. Skip examples and evidence

2. Which answer would show stronger understanding of Reaction Quotient Q — Predicting Direction of Shift?

A. An answer with accurate terms and reasoning

B. A copied definition only

C. A single-word response

D. An answer with no example

3. What should you do if a question asks you to explain?

A. Link the idea to a reason or cause

B. List unrelated facts

C. Only draw a diagram

D. Write the shortest possible answer

8. Success Criteria Proof

Finish with evidence that you can do each success criterion.

Success criterion 1

Prove that you can: The definition of reaction quotient Q and how it differs from Keq

Band 32 marks
Success criterion 2

Prove that you can: The Q vs Keq decision rule: Q > Keq shifts left, Q < Keq shifts right, Q = Keq means no net change

Band 43 marks
Success criterion 3

Prove that you can: How to calculate Q using the same algebraic expression as Keq but with current concentrations

Band 54 marks

One thing I still need help with: