Acid rain takes place dur to combination of acidic oxides with water and it is an envirronmental concern all over the world. Assuming rain water is uncontaminated with `HNO_(3)` or `H_(2)SO_(4)` and is in equilibrium with `1.25 xx 10^(-4)` atm `CO_(2)`. The Henry's law constant `(K_(H))` is `1.25 xx 10^(6) "torr". K_(a_(1))` of `H_(2)CO_(3) = 4.3 xx 10^(-7)`
Given : `K_(f)CuCI^(Theta) = 1.0 (K_(f)` is formation constant of `CuCI^(o+))`
If `SO_(2)` content is the atomsphere is `0.64 "ppm"` by volume, `pH` of rain water is (assume `100%` ionisation of acid rain as monobasic acid).

Options

A. `4.0`
B. `5.0`
C. `6.0`
D. `7.0`

Answer

B

Explanation

`0.64 "ppm" = 0.64g is 10^(6)mL`.
`= (0.64 xx 10^(3)mL)/(64xx10^(6)mL) = 10^(-5)M (Mw SO_(2) = 64)`
`[H^(o+)] = [SO_(2)] = 10^(-5)M`
`pH = 5.0`