Science 9 · Unit 8: Rates of reaction · Cambridge Lower Secondary Science Stage 9

Questions

1. 1. On a graph of gas volume against time, how can you tell when the reaction is fastest?

   • where the line is steepest
   • where the line is highest
   • where the line is flat
   • at the end of the line
   Check

2. 2. The graph shows the hydrogen given off when magnesium ribbon is added to hydrochloric acid. When is the rate of reaction greatest?

   • it is the same throughout
   • between 0 and 100 seconds
   • between 250 and 350 seconds
   • between 150 and 250 seconds
   Check

3. 3. The graph shows the hydrogen given off when magnesium ribbon is added to hydrochloric acid. When is the rate of reaction lowest?

   • between 250 and 350 seconds
   • between 150 and 250 seconds
   • between 0 and 100 seconds
   • it is the same throughout
   Check

4. 4. Use the graph. About how much hydrogen is produced between 0 and 100 seconds?

   • about 66 cm³
   • about 10 cm³
   • about 37 cm³
   • about 100 cm³
   Check

5. 5. Use the graph. About how much hydrogen is produced between 150 and 250 seconds?

   • about 52 cm³
   • about 14 cm³
   • about 66 cm³
   • about 100 cm³
   Check

6. 6. What is the word equation for magnesium + hydrochloric acid?

   • magnesium + hydrochloric acid → magnesium hydroxide + chlorine
   • magnesium + hydrochloric acid → magnesium chloride + hydrogen
   • magnesium + hydrochloric acid → magnesium chloride + water
   • magnesium + hydrochloric acid → magnesium oxide + water
   Check

7. 7. Why did Sofia repeat her experiment three times?

   • because the first one worked
   • to check her results and calculate a reliable mean
   • to make the reaction faster
   • to use up the acid
   Check

8. 📖 This question is about a text that students read in the app.

   8. What is the mean volume of gas Sofia collected at 20 s?

   • 31 cm³
   • 90 cm³
   • 28 cm³
   • 30 cm³
   Check

9. 📖 This question is about a text that students read in the app.

   9. What is the mean volume of gas Sofia collected at 40 s?

   • 43 cm³
   • 42 cm³
   • 129 cm³
   • 48 cm³
   Check

10. 📖 This question is about a text that students read in the app.

    10. What is the mean volume of gas Sofia collected at 60 s?

    • 57 cm³
    • 166 cm³
    • 53 cm³
    • 55.3 cm³
    Check

11. 📖 This question is about a text that students read in the app.

    11. When did Sofia's reaction end?

    • at about 80 s
    • at 20 s
    • at 40 s
    • it never ended
    Check

12. 📖 This question is about a text that students read in the app.

    12. When was Sofia's reaction fastest?

    • between 80 and 100 seconds
    • between 40 and 60 seconds
    • between 0 and 20 seconds
    • between 60 and 80 seconds
    Check

13. 13. What is the symbol equation for magnesium + hydrochloric acid?

    • Mg + 2HCl → MgCl₂ + H₂O
    • Mg + HCl → MgCl + H
    • Mg + Cl₂ → MgCl₂
    • Mg + 2HCl → MgCl₂ + H₂
    Check

14. 14. Marcus collects hydrogen in an upturned measuring cylinder. Which is a source of error?

    • The acid is too cold to see.
    • The magnesium is too shiny.
    • Some gas escapes before the bung is put in.
    • The cylinder is too accurate.
    Check

15. 📖 This question is about a text that students read in the app.

    15. What was the average rate of Marcus's reaction between 30 and 60 seconds?

    • 18 cm³/s
    • 0.27 cm³/s
    • 8 cm³/s
    • 0.6 cm³/s
    Check

16. 📖 This question is about a text that students read in the app.

    16. What was the average rate of Marcus's reaction between 150 and 180 seconds?

    • 3 cm³/s
    • 0.1 cm³/s
    • 0.27 cm³/s
    • 36 cm³/s
    Check

17. 📖 This question is about a text that students read in the app.

    17. What does the flat part of Marcus's graph, from 270 s, mean?

    • More magnesium was added.
    • The reaction has stopped.
    • The gas is escaping.
    • The reaction is fastest.
    Check

18. 18. Use collision theory. Why does the rate of reaction slow down as the reaction goes on?

    • There are fewer reactant particles left to collide.
    • The particles get bigger.
    • The temperature rises.
    • The gas pushes the particles apart.
    Check