Learners' AlleyDesigned by Khow Willard

Rate of Reactions

Set AFoundations

Name

Time 30 minutes

Total 13 marks

Use a copy of the Periodic Table where you need one.

From the lesson

7 marks

Marble chips react with excess dilute hydrochloric acid. Why does the graph of volume of gas against time level off?

AThe catalyst has been used up.

BThe marble chips have all reacted.

CThe acid has evaporated.

DThe gas has stopped dissolving.

Answer [1]

Source: Learners' Alley, Rate of Reactions slides

Which change does not increase the rate of reaction between marble chips and dilute hydrochloric acid?

Ausing powdered marble

Bwarming the acid

Cusing a larger volume of the same acid

Dusing more concentrated acid

Answer [1]

Source: Learners' Alley, Rate of Reactions slides

Answer these questions about rates of reaction.

(a)

Name two quantities that can be measured to follow the rate of a reaction that gives off a gas.

[1]

(b)

What is an effective collision?

[1]

(c)

Define a catalyst.

[1]

(d)

Explain why a higher temperature increases the rate of a reaction.

[2]

Source: Learners' Alley, Rate of Reactions slides

Practice

6 marks

For which reaction is pressure least likely to affect the speed of reaction?

AC(s) + CO₂(g) → 2CO(g)

BC₂H₄(g) + Br₂(l) → C₂H₄Br₂(l)

C2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)

D2SO₂(g) + O₂(g) → 2SO₃(g)

Answer [1]

Source: 2024 AMKSS Prelim P1 Q31

Potassium chlorate decomposes when heated: 2KClO₃(s) → 2KCl(s) + 3O₂(g). Manganese(IV) oxide is a catalyst. In experiment 1, powdered manganese(IV) oxide is heated with 0.1 g of powdered potassium chlorate. In experiment 2, lumps of manganese(IV) oxide are heated with 0.2 g of powdered potassium chlorate. What are the initial rate and the final volume of oxygen in experiment 2, compared with experiment 1?

	initial rate of reaction	final volume of oxygen formed
A	faster than experiment 1	larger than experiment 1
B	faster than experiment 1	same as experiment 1
C	slower than experiment 1	larger than experiment 1
D	slower than experiment 1	same as experiment 1

Answer [1]

Source: 2024 SJI Prelim P1 Q31

Aqueous hydrogen peroxide decomposes at room temperature to form water and oxygen. It decomposes faster when it is warmed and kept at 50 °C.

Use ideas about collisions between particles to explain why.

[2]

Source: AES Prelim P2 A2(c)

Catalysts are used to speed up many reactions.

Explain, in terms of collisions and energy, the effect of a catalyst on the rate of a reaction.

[2]

Source: 2024 QTSS Prelim P2 A9(a)