Question

In 2017, the concentration of CO2 in the atmosphere reached 405 ppm (pCO2 = 4.05×10-4 atm). The pH of ocean water in 2017 was 8.10. If the atmospheric concentration of CO2 continues to increase at a rate of 2.3 ppm/year, what pH do you expect to observe in the oceans in the year 2037? You may assume that [HCO3-] ≈ constant because the oceans are well-buffered.

Answer 1

Concentration of CO₂ in 2017 = 405ppm with a partial pressure of 4.0510^-4.

It is increasing every year by the rate of 2.3 ppm/year.

So, In the year 203 , 20 years will be passed and thus the CO₂ concentration will be increased by 2.320 = 46ppm.

Thus final concentration = 451 ppm. final Partial pressure = 4.0510^-4. = 4.5110^-4

Let the initial concentration of CO ₂ in the ocean water be C₁ and final be C₂.

Then by Henry's law ,

C₁ = K_HP₁ , Partial pressure of CO₂ = 4.0510^-4 atm.

C₂ = K_HP₂, Partial Pressure of CO₂ = 4.5110^-4atm.

Thus , C₂ = = 1.11 C₁.

Now , pH = . Since concentration of HCO3^-,is constant.

Thus , [H⁺]_{​​​​​​​finally} = [H⁺]_{​​​​​​​initally}

= 10^-8.11.11 = 8.8110^-9.

So, pH = 8.054.