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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