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WAEC Chemistry 2021 Objective — Question 9

Question 9 of 50 from the West African Examinations Council (WAEC) Chemistry 2021 Objective paper, with the correct answer and a full explanation.

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9. Study the graphs below (I, II, III, IV) and use them to answer questions 9 to 11. Which of the graphs illustrates the variation of the rate of evolution of a gas from a given length of magnesium ribbon (y-axis) with increase in the concentration of the acid added (x-axis)?

Diagram for question 9
  • A. I
  • B. IICorrect
  • C. III
  • D. IV

Explanation

As acid concentration increases, the rate of gas evolution increases and levels off — the shape shown in graph II.

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