Unit 5: Reactivity 2: How Much, How Fast and How Far?
Topic 5.3: How Far? The Extent of Chemical Change Questions
Practice 6 exam-style questions for IB Chemistry Topic 5.3. Review the question stems below, then unlock the full Question Bank to access markschemes, model answers, and AI grading.
1State1 mark
• Aimnova practice
Write the equilibrium constant expression, Kc, for the equilibrium 2NO(g) + O2(g) ⇌ 2NO2(g).
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Unlock Question2State2 marks
• Aimnova practice
A reversible reaction is left in a sealed flask at constant temperature until no further change is observed.
State two features of a system that has reached dynamic equilibrium. [2]
State two features of a system that has reached dynamic equilibrium. [2]
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Unlock Question3Predict3 marks
• Aimnova practice
Methanol is made industrially by CO(g) + 2H2(g) ⇌ CH3OH(g), which is exothermic in the forward direction.
Predict, with a reason, the effect of (i) increasing the pressure and (ii) raising the temperature on the equilibrium yield of methanol. [3]
Predict, with a reason, the effect of (i) increasing the pressure and (ii) raising the temperature on the equilibrium yield of methanol. [3]
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Unlock Question4Deduce3 marks
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A sealed flask contains the equilibrium 2NO2(g) ⇌ N2O4(g), where brown NO2 forms colourless N2O4.
Cooling the flask makes the mixture turn paler.
Deduce, with a reason, whether the forward reaction is exothermic or endothermic, and state the effect of cooling on Kc. [3]
Cooling the flask makes the mixture turn paler.
Deduce, with a reason, whether the forward reaction is exothermic or endothermic, and state the effect of cooling on Kc. [3]
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Unlock Question5Explain3 marks
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Hydrogen and iodine reach equilibrium in a sealed container: H2(g) + I2(g) ⇌ 2HI(g), where I2 vapour is purple.
Explain why the colour of the mixture becomes constant once equilibrium is reached, even though the reaction has not stopped. [3]
Explain why the colour of the mixture becomes constant once equilibrium is reached, even though the reaction has not stopped. [3]
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Unlock Question6Calculate3 marks
• Aimnova practice
At a certain temperature, 1.0 mol of N2O4 is placed in a 2.0 dm³ flask and allowed to reach the equilibrium N2O4(g) ⇌ 2NO2(g).
At equilibrium 0.60 mol of N2O4 remains.
Calculate the value of Kc for this equilibrium. [3]
At equilibrium 0.60 mol of N2O4 remains.
Calculate the value of Kc for this equilibrium. [3]
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