Question

Calculate the pH and the equilibrium concentrations of HC2O4- and C2O42- in a 0.0782 M oxalic...

Calculate the pH and the equilibrium concentrations of HC2O4- and C2O42- in a 0.0782 M oxalic acid solution, H2C2O4 (aq).

For H2C2O4, Ka1 = 5.9×10-2 and Ka2 = 6.4×10-5

pH =_______
[HC2O4-] =___________ M
[C2O42-] =___________ M
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Answer #1

Oxalic acid ionizes as

HCOOH HCOOH + H2O ----------> HC2O4- + H3O+

Ka1= [HC2O4-][H3O+]/[H2C2O4]=5.9*10-2

preparing the ICE table

componen                     initial concentration (M)       change in concentration(M)          Equilibrium concentration(M)

H2C2O4                            0.0782                                     -x                                             0.0782-x

HC2O4-                                 0                                           x                                                   x

H3O+                                     0                                          x                                                     x

Ka1= x2/0.0782-x)= 0.059, when sovled for x, x= [H3O+]= 0.0446, [HC2O4-]= 0.0446 and H2C2O4= 0.0782-0.0446= 0.0336

[HC2O4-] undergoes further ionization as HC2O4-+ H2O --------->C2O4-+ H3O+

Ka2= [H3O+][C2O4-]/[HC2O4-] = 6.4*10-5

let x= drop in concentration of HC2O4- to reach equilibrium, at Equilibrium,[H3O+]= [C2O4-]=x

preparing the second ICE Table , x2/(0.0446-x)= 6.4*10-5, when solved for x, x= [H3O+]= 0.00166 and [C2O4-]= 0.00166

total of [H3O+]= 0.00166+0.0446=0.04626, pH= -log [H3O+]= 1.33

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Answer #2
Hòa tan 535 mL khí HCl (ở điều kiện 26,5 oC và 747 mmHg) vào lượng nước vừa đủ để tạo thành 625mL dung dịch. Tính pH của dung dịch trên
answered by: Nguyễn Thị Mỹ Kiều
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