Chemistry - 4CH1 PearsonEdexcel

Reversible Reactions And Equilibria

Overview

Not every chemical reaction runs to completion. Some reactions can go forward and backward at the same time, reaching a state of balance where both reactants and products coexist. Controlling this balance is the key to industrial processes like ammonia production.

In this lesson you will learn what makes a reaction reversible, how dynamic equilibrium is established in a sealed system, and how changing temperature or pressure shifts the position of equilibrium. You will also see why a catalyst speeds up both directions equally without changing the final balance.

Objectives

  1. 3.18 know that some reactions are reversible and this is indicated by the symbol ⇌ in equations describe reversible reactions such as the dehydration of hydrated copper(II) sulfate and the effect of heat on ammonium chloride
  2. know that a reversible reaction can reach dynamic equilibrium in a sealed container
  3. know that the characteristics of a reaction at dynamic equilibrium are: - the forward and reverse reactions occur at the same rate - the concentrations of reactants and products remain constant.
  4. understand why a catalyst does not affect the position of equilibrium in a reversible reaction
  5. know the effect of changing either temperature or pressure on the position of equilibrium in a reversible reaction: - an increase (or decrease) in temperature shifts the position of equilibrium in the direction of the endothermic (or exothermic) reaction - an increase (or decrease) in pressure shifts the position of equilibrium in the direction that produces fewer (or more) moles of gas References to Le Chatelier's principle are not required

Lesson Note

Heat blue copper(II) sulfate crystals and they turn into a white powder as water is driven off. Add water to the white powder and it turns blue again, releasing heat. The same reaction can run in either direction depending on the conditions. This is a reversible reaction, and it is far more common than you might expect.

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Lesson Evaluation

Congratulations on completing the lesson on Reversible Reactions And Equilibria. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.

You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.

Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.

  1. Dynamic equilibrium can only be established in: A) An open container B) A sealed container C) A vacuum D) A heated container Answer: B
  2. At dynamic equilibrium: A) All reactions have stopped B) The concentrations of reactants and products are equal C) The forward and reverse reactions occur at the same rate D) Only the forward reaction occurs Answer: C
  3. Increasing temperature shifts equilibrium towards: A) The exothermic direction B) The endothermic direction C) The side with more moles of gas D) The catalyst Answer: B
  4. A catalyst affects equilibrium by: A) Shifting it to the right B) Shifting it to the left C) Not changing the position but reaching it faster D) Increasing the yield of product Answer: C
  5. In the reaction N2(g) + 3H2(g) = 2NH3(g), increasing pressure shifts equilibrium to the: A) Left (more moles of gas) B) Right (fewer moles of gas) C) No change D) Cannot be predicted Answer: B

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Available on the Green Bridge App

Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.

Full lesson notes with diagrams
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Study offline, anytime, anywhere
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