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In: Chemistry

For a titration of 100m of 1.0M HCN, you added so far 98ml of 1.0M NaOH....

For a titration of 100m of 1.0M HCN, you added so far 98ml of 1.0M NaOH. Have you reached the equivalence point? If not what is the current pH? Ka for HCN =

4.5 x 10^-4

Solutions

Expert Solution

   HCN + NaOH ------------> NaCN + H2O

no of moles of HCN = molarity * volume in L

                                = 1*0.1 = 0.1moles

no of moles of NaOH = molarity * volume in L

                                   = 1*0.098   = 0.098moles

                HCN + NaOH ------------> NaCN + H2O

I             0.1        0.098                     0    

C            -0.098 -0.098                    0.098

E              0.002     0                         0.098

      Pka = -logKa

              = -log4.5*10^-4

              = 3.3467

PH   = PKa + log[NaCN]/[HCN]

          = 3.3467+ log0.098/0.002

         = 3.3467+1.69   = 5.0367 >>>>answer

queen_honey_blossom answered 2 years ago
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