plumiEquilibria: OCR GCSE Combined Science A questions
Every OCR GCSE Combined Science A exam question on C5.2 Equilibria, 2018–2025, with its mark scheme and examiner’s report.
Paper
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Exam
All years
Calculations
- Your answer
- Your answer
Q13(b)(i)
The whole paper ↗Q13(b)(ii)
The whole paper ↗Q13(c)(i)
The whole paper ↗Q13(c)(ii)
The whole paper ↗- Your answer
Q11(a)
The whole paper ↗Q16(a)
The whole paper ↗Q16(b)(i)
The whole paper ↗Q16(b)(ii)
The whole paper ↗Q16(b)(iii)
The whole paper ↗Q16(c)
The whole paper ↗Q16(d)
The whole paper ↗- Your answer
- Your answer
Q16(a)
The whole paper ↗Q16(b)(i)
The whole paper ↗Q16(b)(ii)
The whole paper ↗
All 41 questions on Equilibria, as a list
- June 2025, Chemistry Paper 4 Foundation, Q9 (1 mark): The equation shows a reaction that has reached dynamic equilibrium. N2(g) + 3H2(g) 2NH3(g) Which statement explains why this reaction is a dynamic equilibrium?
- June 2025, Chemistry Paper 10 Higher, Q1 (1 mark): The equation shows a reaction that has reached dynamic equilibrium. N2(g) + 3H2(g) 2NH3(g) Which statement explains why this reaction is a dynamic equilibrium?
- June 2025, Chemistry Paper 10 Higher, Q14 (6 marks): 14* Hydrogen is an important chemical used in industry. Hydrogen is produced when methane and steam are left to reach a dynamic equilibrium. CH4(g) + H2O(g) CO(
- June 2024, Chemistry Paper 4 Foundation, Q13(b)(i) (1 mark): Describe how the word equation shows that the reaction is reversible. [1]
- June 2024, Chemistry Paper 4 Foundation, Q13(b)(ii) (1 mark): The word equation for the forward reaction is: nitrogen + hydrogen ammonia Write the word equation for the backward reaction. [1]
- June 2024, Chemistry Paper 4 Foundation, Q13(c)(i) (2 marks): Plot the data from the table on the graph. [2] The first two points are already plotted.
- June 2024, Chemistry Paper 4 Foundation, Q13(c)(ii) (1 mark): Draw the curve of best fit. [1] 80 70 60 50 Percentage of ammonia 40 (%) 30 20 10 0 0 100 200 300 400 500 600 Pressure (atmospheres)
- June 2024, Chemistry Paper 10 Higher, Q10 (1 mark): Methanol, CH3OH, can be made by reacting carbon monoxide, CO, with hydrogen, H2. CO(g) + 2H2(g) CH3OH(g) The forward reaction is exothermic. Which change in tem
- June 2023, Chemistry Paper 4 Foundation, Q11(a) (1 mark): The reversible reaction. [1]
- June 2023, Chemistry Paper 10 Higher, Q16(a) (1 mark): Complete the equation for this reaction. Fe3+(aq) + SCN–(aq) FeSCN2+(aq) yellow colourless red [1]
- June 2023, Chemistry Paper 10 Higher, Q16(b)(i) (2 marks): Plot the results from the table on the graph. Two points have already been plotted for [2] you.
- June 2023, Chemistry Paper 10 Higher, Q16(b)(ii) (1 mark): Draw a line of best fit. [1] 0.105 0.100 Concentration of 0.095 Fe3+(aq) ions (mol / dm3) 0.090 0.085 0.080 0 30 60 90 120 150 180 210 Time (seconds)
- June 2023, Chemistry Paper 10 Higher, Q16(b)(iii) (2 marks): What is the time it takes for the reaction to reach equilibrium? Give a reason for your answer. Time to reach equilibrium = seconds Reason [2]
- June 2023, Chemistry Paper 10 Higher, Q16(c) (2 marks): A student increases the concentration of SCN–(aq) ions in the mixture. The mixture turns darker red. Use Le Chatelier’s principle to explain the change in colou
- June 2023, Chemistry Paper 10 Higher, Q16(d) (2 marks): The student thinks that the forward reaction shown in (a) for the equilibrium is exothermic. Describe what the student should do to the equilibrium mixture to s
- June 2022, Chemistry Paper 4 Foundation, Q4 (1 mark): Nitrogen, N2, reacts with hydrogen, H2, to make ammonia, NH3. N2 + 3H2 2NH3 What is the name of this type of reaction? A Combustion B Electrolysis C Neutralisat
- June 2022, Chemistry Paper 10 Higher, Q7 (1 mark): Sulfur dioxide, SO2, reacts with oxygen, O2, to make sulfur trioxide, SO3, to form a dynamic equilibrium. 2SO2 + O2 2SO3 Which statement describes the reaction
- June 2022, Chemistry Paper 10 Higher, Q16(a) (2 marks): State Le Chatelier’s principle. [2]
- June 2022, Chemistry Paper 10 Higher, Q16(b)(i) (1 mark): As the temperature of the reaction is increased does the amount of ethanol decrease, increase or stay the same? [1]
- June 2022, Chemistry Paper 10 Higher, Q16(b)(ii) (2 marks): Explain your answer to (b)(i). [2]
- June 2022, Chemistry Paper 10 Higher, Q16(c)(i) (1 mark): As the pressure of the reaction is increased does the amount of ethanol decrease, increase or stay the same? [1]
- June 2022, Chemistry Paper 10 Higher, Q16(c)(ii) (2 marks): Explain your answer to (c)(i). [2]
- November 2021, Chemistry Paper 4 Foundation, Q14(c)(ii) (2 marks): The student adds a few drops of water to a boiling tube containing some of the white solid. Describe what the student observes happening to the white solid. Giv
- November 2021, Chemistry Paper 10 Higher, Q17(a)(i) (1 mark): Fig. 17.1 shows how the reaction rate of the forward and backward reactions change as the equilibrium is reached. Forward reaction Reaction rate Backward reacti
- November 2021, Chemistry Paper 10 Higher, Q17(a)(ii) (1 mark): Fig. 17.2 shows how the concentrations of NO2(g) and N2O4(g) change as the equilibrium is reached. Concentration Concentration of N2O4(g) Concentration of NO2(g
- November 2021, Chemistry Paper 10 Higher, Q17(b)(i) (1 mark): Write the letter, A–E, of one equation where more product is formed when the temperature is decreased. [1]
- November 2021, Chemistry Paper 10 Higher, Q17(b)(ii) (1 mark): Write the letter, A–E, of one equation where the amount of product is unchanged when the pressure is increased. [1]
- November 2021, Chemistry Paper 10 Higher, Q17(b)(iii) (1 mark): Write the letter, A–E, of one equation where more product is formed when either the temperature is increased or when the pressure is decreased. [1]
- November 2020, Chemistry Paper 4 Foundation, Q3 (1 mark): The reaction to make sulfur trioxide, SOz, is an example of a dynamic equilibrium. The equation is shown below. 250½(9) +29} 2503(g) Which symbol completes the
- November 2020, Chemistry Paper 10 Higher, Q16 (6 marks): 16* Nitrogen and hydrogen react to form ammonia in a dynamic equilibrium. N2(g) + 3H2(g) 2NH3(g) ∆H = −92 kJ / mol The table shows the amount of ammonia formed
- June 2019, Chemistry Paper 4 Foundation, Q12(a) (1 mark): In a closed system the reaction between sulfur dioxide and oxygen reaches a dynamic equilibrium. Use a symbol from the list to complete the sentence. > < = 1 2
- June 2019, Chemistry Paper 4 Foundation, Q12(b) (1 mark): What is meant by the term reversible reaction? [1]
- June 2019, Chemistry Paper 10 Higher, Q6 (1 mark): Reversible reactions in a closed system reach a dynamic equilibrium. At equilibrium, which statement is correct? A rate of reverse reaction = 0 B rate of forwar
- June 2019, Chemistry Paper 10 Higher, Q15(b) (1 mark): The equilibrium position of reversible reactions may be altered by changing the reaction conditions, such as temperature and pressure. Write down one other cond
- June 2019, Chemistry Paper 10 Higher, Q15(c)(i) (2 marks): When the reaction between sulfur dioxide and oxygen is at equilibrium, what is the effect of increasing the temperature? Explain your answer. [2]
- June 2019, Chemistry Paper 10 Higher, Q15(c)(ii) (2 marks): When the reaction between sulfur dioxide and oxygen is at equilibrium, what is the effect of increasing the pressure? Explain your answer. [2]
- June 2018, Chemistry Paper 4 Foundation, Q6 (1 mark): Look at the equation for the reaction between nitrogen and hydrogen to make ammonia. N2(g) + 3H2(g) 2NH3(g) The reaction forms a dynamic equilibrium. Which of t
- June 2018, Chemistry Paper 10 Higher, Q3 (1 mark): Look at the equation for the reaction between sulfur dioxide and oxygen to make sulfur trioxide. 2SO2(g) + O2(g) 2SO3(g) The reaction forms a dynamic equilibriu
- June 2018, Chemistry Paper 10 Higher, Q18(a) (2 marks): Predict the effect of adding more oxygen to the equilibrium mixture. Explain your answer. [2]
- June 2018, Chemistry Paper 10 Higher, Q18(b) (2 marks): Predict the effect of increasing the total pressure in the equilibrium mixture. Explain your answer. [2]
- June 2018, Chemistry Paper 10 Higher, Q18(c) (2 marks): Predict the effect of increasing the temperature of the equilibrium mixture. Explain your answer. [2]
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