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WAEC Chemistry 2025 Objective — Question 15

Question 15 of 50 from the West African Examinations Council (WAEC) Chemistry 2025 Objective paper, with the correct answer and a full explanation.

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In the use of a universal indicator, red colour is an indication that the substance is a

  • A. concentrated acidCorrect
  • B. concentrated alkali
  • C. dilute acid
  • D. dilute base

Explanation

The universal indicator is a pH indicator composed of a mixture of several different indicators that show different colours at different pH levels. In an acidic solution, the pH is below 7, and the universal indicator will shift toward red or orange depending on the strength of the acid; a strong (concentrated) acid gives red.

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