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

\begin{array}{l} = \frac{(60 - 0) {cm}^{3}}{120 s} \\ = \frac{60 {cm}^{3}}{120 s} \\ = 0.50 {cm}^{3} s^{-1} \end{array}

(b)
Average rate of reaction in the second minute

\begin{array}{l} = \frac{(60 - 40) {cm}^{3}}{(120 - 60) s} \\ = \frac{20 {cm}^{3}}{60 s} \\ = 0.33 {cm}^{3} s^{-1} \end{array}

(c)
Average rate of reaction for the whole reaction

\begin{array}{l} = \frac{65 {cm}^{3}}{150 s} \\ = 0.43 {cm}^{3} s^{-1} \end{array}

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