O https 17977 CH15HW dohertym21738@mail.sacredheart.edu 03/15/18 This is a Numer

Question

O https 17977 CH15HW dohertym21738@mail.sacredheart.edu 03/15/18 This is a Numeric Entry question/It is worth 1 point/You have unllmited attempts/There is no attempt penalty 14 Question ( point) aSee page 764 v 4th attempt See Periodic Table See Hint 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 pKa1-1.23 and pKa2-4.19, what is the pH of a 0.0232 Msolution of oxalic acid? 3rd attempt 13 OF 17QUESTIONS COMPLETED + VIEW SOLUTION SUBMIT ANSWER MacBook Air

Explanation / Answer

H2 C2 O4 --------> H + + H C2 04 -

0.0232-x ................x ...............x

=> x^2 / ( 0.0232 - x ) = Ka

=> => x^2 / ( 0.0232 - x ) = 10^(-1.23)

=> x^2 / ( 0.0232 - x) = 0.0588

=>x = 0.0177

H C2 O4- ---------> H+ + C2 04 2-

0.0177-x ..............x+0.0177 ........x

=> (x)(x+0.0177) / ( 0.0177 - x ) = Ka2

=> ( x^2 + 0.0177x ) / ( 0.0177 - x ) = 10^(-4.19)

=> ( x^2 + 0.0177x ) / ( 0.0177 - x ) = 6.4565 x 10^-5

=> x^2 + 0.0177 x = - 6.4565 x 10^-5 x + 1.143 x 10^-6

=> x^2 + 0.017764x - 1.143 x 10^-6 = 0

=>x = 6.411 x 10^ -5

so pH = - log ( 6.411 x 10^ -5 + 0.0177 )= - log ( 0.017764)

=> pH = 1.75

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