Chemistry, asked by Harshchacharkar8213, 1 year ago

The average concentration of SO2 in the atmosphere over a city on a certain day is 10 ppm. when the average temperature is 298 K. Given that the solubility of SO2 in water at 298 K is 1.3653 moles litre–1 and the pKa of H2SO3 is 1.92, estimate the pH of rain on that day.

Answers

Answered by nsopagu
10
We have, as concentration of SO2 in air is 10 ppm or 10×10–6 mole in 1 mole air or 10–5 mole of SO2 per mole of air. The concentration of SO2 in air is substantial and since rain water is falling from enormously great height , and hence each drop of rain water will get saturated with SO2 before it reaches the earth.

Therefore,                          [SO2]     =             [H2SO3]                =             1.3653 mol/litre

As,                                          SO2 +             H2O        →           H2SO3

Also,                                      H2SO3 ↔          2H+ +             SO32–

C                                             0                              0

C – a/2                                  a                              a/2

Therefore,                          Ka =             a2.a/[2×(C – a/2)]

10–1.92 =             a3/2C                     [As, C = 1.3653]

Therefore,                                          a              =             [1.3653×2×10–1.92]1/3

=             [H+]

Therefore,                                          pH          =             – log a

=             0.49               [Ans.]

 

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