Environmental Chemistry - Result Question 20

20. The $pH$ of rain water, is approximately

(2019 Main, 9 Jan II)

(a) 7.5

(b) 6.5

(c) 5.6

(d) 7.0

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Answer:

Correct Answer: 20. (c)

Solution:

  1. In clean air, rain water picks up some acidic oxides like $CO _2$ and $SO _2$ (obtained from volcanic eruptions). These substance make the rain slightly acidic $(pH=5.6-6)$.