Triple science: iGCSE Chemistry Only |
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Q1-2:
The energy level diagram for a reaction with and without a catalyst is shown below:
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1. Which letter represents the activation energy for the uncatalysed reaction? |
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2. Which letter represents the activation energy for the catalyzed reaction? |
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Q3-4:
An energy level diagram for a reaction is shown here:
3. Which type of energy change does this diagram represent and what sign should ΔH be given? |
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Type of change |
Sign of ΔH |
A |
exothermic |
positive |
B |
exothermic |
negative |
C |
endothermic |
positive |
D |
endothermic |
negative |
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4.For which reaction(s) would this be an appropriate diagram?
I. CH4 + 2O2 → CO2 + 2H2O |
II. C + O2 → CO2 |
III. 2H2+ O2 → 2H2O |
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- A. all of them
- B. I and II only
- C. II and III only
- D. none of them
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5. Which of the following statements about catalysts are true? A catalyst..
I. provides an alternative pathway with lower activation energy |
II. provides an alternative pathway with a lower enthalpy change |
III. is chemically unchanged at the end of the reaction |
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- A. I and II
- B. I and III
- C. II and III
- D. all of them
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6. Which of the following is correct about the energy changes involved during bond breaking and bond making?
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Bond breaking |
Bond making |
A |
exothermic |
endothermic |
B |
exothermic |
exothermic |
C |
endothermic |
endothermic |
D |
endothermic |
exothermic |
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7. For the reaction:
R2 + S2 → 2RS
Which combination of bond strengths would produce the most exothermic reaction?
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Bond strength in R2 and S2 |
Bond strength in RS |
A |
weak |
weak |
B |
weak |
strong |
C |
strong |
weak |
D |
strong |
strong |
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Q8-10:
The following equation represents the conversion of sulfur dioxide to sulfur trioxide:
Average bond energies for the bonds involved are:
O=O bond 496 kJ/mol
S=O bond 523 kJ/mol |
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8. The energy required to break the bonds in the reactants is..
- A. 1542 kJ/mol
- B. 1569 kJ/mol
- C. 2588 kJ/mol
- D. 3138 kJ/mol
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9. The energy given out when the bonds in the products form is..
- A. 1542 kJ/mol
- B. 1569 kJ/mol
- C. 2588 kJ/mol
- D. 3138 kJ/mol
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10. The enthalpy change, ΔH, for this reaction is..
- A. +550 kJ/mol
- B. -550 kJ/mol
- C. +27 kJ/mol
- D. -27 kJ/mol
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