Worked example
A reaction forms 24 mL of gas in 6 s. What is its average gas-production rate over that interval?
Answer & why
Answer: 4 mL/s
24 mL ÷ 6 s = 4 mL/s.
Grade 11 · Science
Interpret evidence about reaction rates
Use stated controlled comparisons and measured amounts per time to evaluate a reaction-rate claim.
6 authored questions + worked example
Add to plan
All questions
All 6 authored questions for this skill.
Question 1
A trial with catalyst forms 30 mL in 10 s; an otherwise matched trial without it forms 10 mL in 10 s. What do these measurements support?
- Every reaction everywhere has this exact rate.
- Three times as much total reactant was necessarily used.
- The catalyst creates atoms from nothing.
- A greater average gas-production rate with the catalyst in these trials.
A hint
Compare trials that isolate the named factor, and define rate as the measured change per unit time.
Answer & why
Answer: A greater average gas-production rate with the catalyst in these trials.
The observed averages are 3 mL/s and 1 mL/s under the stated conditions.
Question 2
Three matched trials produce rates of 2.9, 3.0 and 3.1 mL/s. Which report preserves the measured variation?
- Only the largest result existed.
- Rates ranged from 2.9 to 3.1 mL/s.
- No variation occurred.
- Every rate was exactly 10 mL/s.
A hint
Compare trials that isolate the named factor, and define rate as the measured change per unit time.
Answer & why
Answer: Rates ranged from 2.9 to 3.1 mL/s.
The range includes all three stated results.
Question 3
A student changes both surface area and temperature and observes a faster reaction. What cannot be isolated from this comparison alone?
- That two factors were changed.
- The separate effect of either changed factor.
- The measured result if it was recorded.
- The names of the changed factors.
A hint
Compare trials that isolate the named factor, and define rate as the measured change per unit time.
Answer & why
Answer: The separate effect of either changed factor.
The simultaneous changes prevent assigning the difference to one factor alone.
Question 4
A reaction produced 20 mL after 5 s and 28 mL after 9 s. What is the average production rate between those readings?
- 7 mL/s
- 8 mL/s
- 2 mL/s
- 48 mL/s
A hint
Compare trials that isolate the named factor, and define rate as the measured change per unit time.
Answer & why
Answer: 2 mL/s
The interval adds 8 mL over 4 s, giving 2 mL/s.
Question 5
A reaction forms 24 mL of gas in 6 s. What is its average gas-production rate over that interval?
- 0.25 mL/s
- 4 mL/s
- 18 mL/s
- 144 mL/s
A hint
Compare trials that isolate the named factor, and define rate as the measured change per unit time.
Answer & why
Answer: 4 mL/s
24 mL ÷ 6 s = 4 mL/s.
Question 6
To test temperature's effect, which comparison isolates temperature: A has the same amounts and concentration at 20°C versus 30°C; B changes temperature and concentration?
- Comparison B
- Neither contains a temperature difference.
- Both isolate only temperature.
- Comparison A
A hint
Compare trials that isolate the named factor, and define rate as the measured change per unit time.
Answer & why
Answer: Comparison A
A changes the named factor while keeping the other stated factors alike.