This question is about reversible reactions and chemical equilibrium - AQA - GCSE Chemistry - Question 6 - 2015 - Paper 3
Question 6
This question is about reversible reactions and chemical equilibrium.
(a) Reversible reactions can reach equilibrium in a closed system.
(i) What is meant by a clo... show full transcript
Worked Solution & Example Answer:This question is about reversible reactions and chemical equilibrium - AQA - GCSE Chemistry - Question 6 - 2015 - Paper 3
Step 1
What is meant by a closed system?
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Answer
A closed system is one where nothing can enter or leave during a reaction. This means that the total mass and energy remain constant, ensuring that the reaction can reach equilibrium without interference from external factors.
Step 2
Explain why, when a reversible reaction reaches equilibrium, the reaction appears to have stopped.
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Answer
At equilibrium, the forward and backward reactions occur at the same rate. Thus, the concentrations of reactants and products remain constant over time, giving the impression that the reaction has stopped, even though it is still occurring.
Step 3
Name a natural resource from which hydrogen is produced.
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Hydrogen is commonly produced from natural gas, which consists primarily of methane (CH₄).
Step 4
Explain how a catalyst speeds up a reaction.
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A catalyst provides an alternative reaction pathway with a lower activation energy, which increases the rate of both the forward and backward reactions, thereby speeding up the overall reaction.
Step 5
What happens to the amount of ammonia produced at equilibrium if the pressure is increased?
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When the pressure is increased, the amount of ammonia produced at equilibrium increases. This occurs because the equilibrium shifts toward the side of the reaction with fewer gas molecules, favoring the formation of ammonia.
Step 6
Draw an arrow to show the activation energy on the diagram in Figure 3.
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The activation energy can be indicated by a vertical arrow starting at the energy level of the reactants (2 HI) and extending to the peak of the energy barrier shown in the diagram.
Step 7
How does the diagram in Figure 3 show that the reaction is endothermic?
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The diagram shows that the energy of the products (H₂ + I₂) is higher than that of the reactants (2 HI), indicating that energy is absorbed during the reaction process, characteristic of an endothermic reaction.
Step 8
Suggest what effect, if any, increasing the temperature will have on the amount of hydrogen iodide at equilibrium.
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If the temperature is increased, the amount of hydrogen iodide will decrease. This occurs because the equilibrium shifts to favor the endothermic reaction, which absorbs heat, thereby reducing the concentration of hydrogen iodide.
