no of moles of ACEs = W/G.M.Wt  = 1.687/220.29 =
0.00765 moles
                       Â
ACES + HCl --------------> HACES
          Â
IÂ Â Â Â Â Â Â Â Â Â
0.00765Â Â Â Â
x                        Â
0
         Â
CÂ Â Â Â Â Â Â Â Â Â
-x           Â
-x                        Â
+x
        Â
EÂ Â Â Â Â Â
0.00765-x    Â
0Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
+x
                   Â
PHÂ Â = PKa + log[HACES]/[ACES]
              Â
7.25Â Â Â = 6.85 + logx/0.00765-x
             Â
7.25-6.85Â Â Â = logx/0.00765-x
              Â
0.4Â Â Â Â Â Â Â Â =
logx/0.00765-x
        logx/0.00765-x
= 0.4
           Â
x/0.00765-x  = 100.4
         Â
x/0.00765-x  = 2.5118
        Â
x                    Â
= 2.5118*(0.00765-x)
                 Â
x          Â
= 0.01921-2.5118x
                Â
x+2.5118x  = 0.01921
                Â
3.5118x     = 0.01921
                        Â
x        = 0.01921/3.5118
= 0.0055moles
              Â
no of moles oc HCl = x = 0.0055moles
                   Â
molarity of HCl  = no of moles/volume in L
                                             Â
= 0.0055/0.01518Â Â = 0.362 M >>>>>>
answer
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