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Chemistry Chapter 8 : Topic 5
Catalysts and Reaction Pathways
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A student observes a reaction energy profile diagram where the energy of products is lower than that of reactants, and energy is released to surroundings. Which conclusion is correct?
Reasoning: In exothermic reactions, products have lower energy than reactants, so excess energy is released.
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In a reaction pathway diagram, the highest point on the curve represents:
Reasoning: The peak represents the transition state where maximum energy is required to form activated complex.
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In a catalyzed reaction pathway diagram, which statement is correct?
Reasoning: A catalyst lowers activation energy by providing an alternate pathway but does not change ΔH.
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A student compares two energy profile diagrams (catalyzed and uncatalyzed). The key difference is:
Reasoning: Catalyst lowers the peak (activation energy) but reactant and product energies remain same.
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A reaction has a large energy difference between reactants and the peak of the curve. This energy difference is known as:
Reasoning: Activation energy is the energy required to reach the transition state from reactants.
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Which of the following correctly describes enthalpy change (ΔH) in a reaction pathway diagram?
Reasoning: ΔH is the energy difference between reactants and products.
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A reaction in which products are at higher energy level than reactants is called:
Reasoning: Endothermic reactions absorb energy, so products have higher energy.
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In an exothermic reaction pathway diagram, the enthalpy change (ΔH) is:
Reasoning: Energy is released, so products are lower in energy than reactants, making (ΔH) negative.
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A catalyst affects a reaction by:
Reasoning: Catalyst provides an alternative pathway with lower activation energy.
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Why does a catalyst not appear in the final energy difference of a reaction diagram?
Reasoning: Catalyst is not consumed and does not affect initial or final energy levels.
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In a reaction energy diagram, the energy gap between reactants and peak represents:
Reasoning: This gap is the energy required to start the reaction.
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Which statement best describes the role of transition state in a reaction pathway?
Reasoning: Transition state is a highly unstable, high-energy configuration.
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A reaction profile shows a small activation energy in presence of catalyst. This means:
Reasoning: Lower activation energy allows more successful collisions per second.
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Which of the following remains unchanged in catalyzed and uncatalyzed reaction diagrams?
Reasoning: Catalyst does not change overall energy difference between reactants and products.
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A student interprets a diagram where energy decreases continuously from reactants to products. This represents:
Reasoning: Continuous decrease shows energy is released.
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Which label is correctly placed at the lowest point on a reaction pathway diagram?
Reasoning: Products lie at final energy level after reaction completion.
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If activation energy is very high, the reaction will:
Reasoning: High energy barrier reduces number of effective collisions.
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Which statement is true about energy profile diagrams?
Reasoning: Reaction pathway diagrams represent energy changes over time.
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In an endothermic reaction, the correct energy relationship is:
Reasoning: Energy is absorbed, so products have higher energy.
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Which of the following best describes activation energy in real-life terms?
Reasoning: It is the threshold energy needed for reaction to begin.
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A catalyst lowers activation energy by:
Reasoning: Catalyst offers an alternative pathway with lower energy barrier.
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If a reaction pathway diagram shows two curves (one high peak and one low peak), the correct interpretation is:
Reasoning: Lower peak represents catalyzed reaction, higher peak is uncatalyzed.
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