Question

Set up the ICE table that you would use to find the pH of a solution that is 0.0025 M HNO3 and 0.10 M lactic acid (HC3H5O3, Ka=1.4× 10–4). Using x as the variable for change, the expression for the concentration of hydrogen ion would be?

Answer 1

HNO3 is strong acid and ionizes completely as HNO3+H2O------->H3O⁺+ NO3-

hecne [H3O+] from HNO3= 0.0025M,

Lactic acid ionizes in water as HC3H5O3+ H2O -------->H3O++ C3H5O3-

Ka= [H3O+] [C3H5O3-]/[C3H5O3]

ICE Table

compound                              initial                          change                              final

lactic acid                            0.1                                     -x                                0.1-x

[H+]                                    0.0025 from HNO3            x                                  0.0025+x

C3H5O3-                           0                                        x                                     x

Ka= x*(0.0025+x)/(0.1-x)= 1.4*10^-4, when solved using excel ,x= 0.00265

[H3O+]= 0.0025+0.00265= 0.00515, pH= -log [H3O+] = 2.288