Formative Practice 4.1 – Form 5 Science (KSSM) Chapter 4


Question 1:
Give one example of a fast reaction and one example of a slow reaction in daily life.

Answer:
Example of a fast reaction: Burning of candle
Example of a slow reaction: Photosynthesis
(any other suitable answer is accepted)


Question 2:
Define rate of reaction.

Answer:
Rate of reaction is the change in the quantity of reactants or products of a reaction per unit time.


Question 3:
Figure 1 shows the graph of volume of hydrogen gas released against time.


Calculate the average rate of reaction:
(a) for the first 2 minutes
(b) in the second minute
(c) for the whole reaction


Answer:
(a)
Average rate of reaction for the first 2 minutes
= (600)  cm 3 120 s = 60  cm 3 120 s =0.50  cm 3 s -1

(b)
Average rate of reaction in the second minute
= (6040)  cm 3 (12060) s = 20  cm 3 60 s =0.33  cm 3 s -1

(c)
Average rate of reaction for the whole reaction
= 65  cm 3 150 s =0.43  cm 3 s -1

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