Exothermic and Endothermic Reactions Quiz
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5 questions, one answer each
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1. Which statement correctly describes an exothermic reaction?
- A. Thermal energy is transferred to the surroundings, causing the temperature to increase
- B. Thermal energy is taken in from the surroundings, causing the temperature to decrease
- C. The enthalpy change (ΔH) is positive
- D. The activation energy is released to the surroundings
2. What does the term 'activation energy' mean?
- A. The total energy released during a reaction
- B. The minimum energy that colliding particles must have in order to react
- C. The energy difference between reactants and products
- D. The energy required to break all bonds in the reactants
3. In terms of bond breaking and making, explain why combustion reactions are exothermic.
- A. More energy is required to break bonds than is released when new bonds form
- B. More energy is released when new bonds form than is required to break the original bonds
- C. Bond breaking and bond making release equal amounts of energy
- D. No bonds are broken during combustion, only new bonds are formed
4. A reaction has ΔH = +85 kJ/mol and Ea = 50 kJ/mol. Which statement is correct?
- A. The reaction is exothermic with an activation energy of 85 kJ/mol
- B. The reaction is endothermic and the products have higher energy than the reactants
- C. The reaction is exothermic because the activation energy is lower than ΔH
- D. The reaction is endothermic because ΔH is negative
5. Calculate the enthalpy change for a reaction using the following bond energy data: Bonds broken: C–H (×4) = 412 kJ/mol, O=O = 498 kJ/mol. Bonds formed: C=O (×2) = 799 kJ/mol, O–H (×2) = 467 kJ/mol.
- A. ΔH = −1356 kJ/mol
- B. ΔH = +1356 kJ/mol
- C. ΔH = −194 kJ/mol
- D. ΔH = +194 kJ/mol