Why does a 10 C rise roughly double the rate?

Warmer particles have more kinetic energy, so a much larger fraction exceeds the activation energy and successful collisions multiply.

What matters in a molar volume question?

Balance the equation to get the mole ratio, then multiply moles by molar volume, keeping cm^3 and dm^3 consistent.

S5 Chemistry Rates of Reaction, Paper 4: average rate, temperature effect and molar volume

2026-11-02

Tutor Prep Guide · Primary English

Ten graded items on gas collection rates, temperature doubling, catalysts, surface area and a molar volume conversion, each with an answer.

Focus　Rate is change over time, ten degrees roughly doubles it, a catalyst lowers activation energy and molar volume links moles to volume.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	25
Difficulty mix	Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1
Chapter	Chapter: S5 Chemistry: Rates of Reaction
Level	Four basic, three advanced, two challenge and one error-repair item

02　Questions (10 items)

Foundation96 cm^3 of hydrogen is collected in 40 s. What is the average rate?
FoundationRate roughly doubles for every 10 C rise. By what factor does it change from 25 C to 55 C?
FoundationHow does a catalyst speed up a reaction?
FoundationEqual masses of limestone powder and limestone chips react with acid of the same concentration. Which is faster?
IntermediateIn the first 30 s the concentration of a reactant falls from 0.80 to 0.50 mol dm^-3. What is the average rate?
IntermediateIn the same reaction, how many times faster is the run at 60 C than the run at 20 C?
IntermediateThe volume against time curve becomes flatter and flatter. What does that show?
Challenge0.240 g of magnesium ribbon (24 g mol^-1) reacts completely with excess dilute acid. What volume of hydrogen is collected at room temperature (24 dm^3 mol^-1)?
ChallengeRun A finishes in 20 s and run B in 80 s. What is the ratio of their average rates, A to B?
Error redoError repair: a student writes that a flat curve means the reaction has stopped and particles no longer collide. What is wrong?

03　Answers and one-line notes

#	Answer	One-line note
1	2.4 cm^3 s^-1	Rate is volume over time, so 96 divided by 40 gives 2.4.
2	Eight times	A rise of 30 C is three steps of 10 C, and doubling three times gives two to the power three.
3	It provides an alternative route of lower activation energy	A catalyst offers a route with a lower activation energy, so a larger fraction of collisions succeed and the rate rises.
4	The powder	The powder has a much larger surface area, so more particles meet the acid at once and the collision frequency is higher.
5	0.0100 mol dm^-3 s^-1	The concentration falls by 0.30, which over 30 s gives 0.0100.
6	Sixteen times faster	The gap of 40 C is four steps of 10 C, so the hotter run is sixteen times faster.
7	The reactant concentration is low, the rate has slowed and the reaction is nearly complete	A flattening curve means less gas is formed each second, not that the reaction has stopped completely.
8	240 cm^3	The magnesium is 0.0100 mol and each mole gives one mole of hydrogen, so 0.0100 times 24 dm^3 is 0.240 dm^3.
9	4 : 1	The shorter run is faster, and 80 divided by 20 is 4, so the first run is four times as fast.
10	The particles still collide, but the low concentration makes collisions rare	Near the end little reactant is left, so collisions become rare and the curve flattens; the particles still collide.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

Book an S5 Chemistry tutor Tutor Registration →

Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.