Answer:
pH of rain with only CO₂ as the acidic pollutant in the atmosphere = 5.58
Explanation:
If other sources of acidity like CO₂, and acidic particles are minimal,
P꜀ₒ₂ = 1 atm × 412ppm = 1 × 412 × 10⁻⁶ = 4.12 × 10⁻⁴ atm
With the CO₂ conc of 412ppm,
Henry's law constant for CO₂, Kₕ = 0.038 M/atm
[CO₂(aq)] = KₕP꜀ₒ₂ = (0.038)(4.12 x 10⁻⁴) = 1.57 x 10⁻⁵ M
Chemical Reaction
CO₂ + H₂0 <-----> H⁺ + HCO₃⁻ Kₐ = 4.45 x 10⁻⁷ (from literature)
Note: although we can not really use an initial change equilibrium table because
CO₂ will not be depleted from the gas phase and CO₂ will he constant, we can expect that [H⁺] = [HCO₃⁻] (assuming no other sources of H⁺
Kₐ = 4.45 x 10⁻⁷ = [H⁺] [HCO₃⁻]/[CO₂] = [H⁺]²/(1.57 x 10⁻⁵)
[H⁺] = √[(4.45 x 10⁻⁷)(1.57 x 10⁻⁵)] = 2.64 x 10⁻⁶ M
pH = -log [H⁺] = - log (2.64 x 10⁻⁶) = 5.58
Hope this Helps!!!
