hi See Periodic Table See Hi The leaves of the rhubarb plant

hi See Periodic Table See Hi The leaves of the rhubarb plant contain high concentrations of diprotic oxalic acid (HOOCCOOH) and must be removed before the stems are used to make rhubarb pie. If pK21 1.23 and pKa2 4.19, what is the pH of a 0.0199 Msolution of oxalic acid? 3 OF 7 QUESTIONS COMPLETED search PAC

Solution

concentration of Oxalic acid= 0.0199M

PKa1= 1.23

- log(Ka1) = 1.23

Ka1= 10^-1.23

Ka1= 0.05888= 5.89x10^-2

HOOCCOOH ---------------------------- HOOCCOO- + H+

0.0199                                             0                0

-x                                                 +x              +x

0.0199 - x                                           +x              +x

Ka1 = [HOOCCOO-][H+]/[HOOCCOOH]

5.89x10^-2 = x*x/(0.0199 - x)

for solving the equation

x= 0.0157

[H+] = 0.0157M

-log[H+] = -log(0.0157)

PH= 1.8

for poly protic acids PH values depends on the PKa1 value only.because Pka2 value is very less.