b) The current (Year 2017) atmospheric CO2 concentration is 370
ppm. It is estimated that if we continue to exploit the world’s
fossil fuel reserves at the same rate, the atmospheric CO2
concentration will reach 1,100 ppm in Year 2400 (Williams,
2001).
Justify your answer in (1) quantitatively by calculating the pHs
when CO2 concentrations are 370 ppm (Year 2017) and 1,100 ppm (Year
2400), respectively. Assuming: I. Pure water is in equilibrium with
CO2 at 25oC.
II. Water vapor pressure is 0.031 atm.
III. Henry’s Law constant 3.38x10-2 (mol/L) x
atm-1 at 25oC for CO2.
IV. Ka1 = 4.45x10-7; Ka2 =
4.69x10-11
Neglect all other processes such as complexation, and
precipitation.
H2O + CO2 <----> H2CO3(aq)
According to the ideal gas equation: PV = nRT, then P = CRT
Where 'C' is the concentration of CO2 = 370 ppm = 370 mg/L = 0.00841 mol/L
Note: Molar mass of CO2, i.e. P(CO2) = 44 g/mol, i.e. moles of CO2 = 370 mg/44 g.mol-1 = 8.41 mol or 0.00841 mmol
Now, pressure of CO2 = 0.00841 mol/L * 0.0821 L.atm/mol.K * (25+273) K = 0.20574 atm
According to the Henry's law:
The concentration of the gas in water = KH * P(CO2) = 3.38*10-2 mol/L.atm * 0.20574 atm = 0.006954 mol/L or 0.006954 M
b) The current (Year 2017) atmospheric CO2 concentration is 370 ppm. It is estimated that if...
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.