Consider the titration of a 23.0?mL sample of 0.110MHC2H3O2 with 0.120M NaOH. De
ID: 839114 • Letter: C
Question
Consider the titration of a 23.0?mL sample of 0.110MHC2H3O2 with 0.120M NaOH. Determine each of the following.
Part A
the initial pH
Express your answer using two decimal places.
Part B
the volume of added base required to reach the equivalence point
Part C
the pH at 6.00mL of added base
Express your answer using two decimal places.
Part D
the pH at one-half of the equivalence point
Express your answer using two decimal places.
Part E
the pH at the equivalence point
Express your answer using two decimal places.
Explanation / Answer
A)let the intial dissociation be x.so,
1.8*10^-5 = x^2/(0.11-x)
or x=1.398*10^-3
so pH=-log(1.398*10^-3)
=2.85
B)equating the number of moles,
23*0.11=0.12*x
or x=21.08 mL
C)pH=pKa+log(salt/acid)
=4.76 + log( 0.12*6/(23*0.11-6*0.12))
=4.36
d)pH of strong base and a weak acid at the equivalence point,
pH=7 +0.5 pKa+log(salt/acid)
=7+0.5*4.76 + log((23*0.11)/(23+21.08))
=8.14