Question

If at some point in the future the concentration of CO2 in the atmosphere is 420 ppm, calculate the pH of pure rain water at this time. Calculate the akalinity of this rain.

Answer 1

PH of the 420 ppm CO2 in water: Equation for the dissolution of CO2 in water is as follows CO2(8) H,oi)H(aq) Concentr ati on of CO2[CO2] 420 ppm 420 ppmx ppm 420 mg L 10 mg 44.01g 9.54x103 mol CO,/L 9.54x103 M Concentration of Н.Са 9.54×10-3 M ICE table constructed is as follows; I(M): 9.54x10 C(M) E(M): (9.54 x 103-X) 1st aci dionizat on constant, K^1- H2CO2 4.3x10%-(x)(x) 9.54 x10--х From the equilibrium table, [H,0 6.4x10-5M = 6.4 x 10-5 M НСОз-]= x ICE table constructed for the 2ndionizati on of H2CO3 is as follows, НСО,-(aq) + H2O(1) CQ"(aq) + H,0+ (aq) 1(M): 6.4×10-5 c(u) E (M) (6.4x10-x) 6.4x10-5 + x 6.4x10x 2nd acidionizati on constant, K - HCO3 (6.4x10*+x)(x) 4.8x10-1 6.4x10-x x4.8x1011 From the equilibrium table, [H,o- (64x10+x)M = (6.4×10-5 +4.8×10-11 s 6.4x10- M pH =-log[Hs0.F-log(64x10") = 4.19