A certain sample of rainwater gives a yellow colour with methyl red [pH range 4.2 (red) – 6.2 (yellow)] and a yellow colour with phenol red [pH range 6.4 (yellow) – 8.0 (red)]. What is the approximate

Question

A certain sample of rainwater gives a yellow colour with methyl red [pH range 4.2 (red) – 6.2 (yellow)] and a yellow colour with phenol red [pH range 6.4 (yellow) – 8.0 (red)]. What is the approximate pH of the water? Is the rainwater acidic, neutral, or basic?

Prashant Kotian · Accepted Answer

Correct answer: A. A yellow color with methyl red means the pH is at or above its upper limit of 6.2. A yellow color with phenol red means the pH is at or below its lower limit of 6.4. Therefore, the pH of the rainwater is bounded between 6.2 and 6.4. The only option fitting this range is 6.3. Since 6.3 < 7.0, the solution is acidic.

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