Question

18. What is the pH of the solution at the equivalence point when 25 ml 0.1M acetic acid is
titrated against 0.1 M NaOH solution.
a) 8.72
b) 7.00
c) 2.83
d) 4.26
Olhaich equation is used to calculate
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Answer 1

Answer:

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Explanation:

• Concentration of sodium acetate =
• 2
• 0.1
• =0.05M at equal volumes of acid and base will be used.
• The equilibrium is,
• CH
• 3
• COO
• −
• +H
• 2
• O⇌CH
• 3
• COOH+OH
• −
• C(1−x) CxCx
• where x, is the degree of hydrolysis and
• K
• h
• =
• (1−x)
• Cx
• 2
• we know that
• K
• h
• =
• K
• a
• K
• w
• =
• 1.9×10
• −5
• 1×10
• −14
• =5.26×10
• −10
• K
• h
• =Cx
• 2
• 5.26×10
• −10
• =0.05×x
• 2
• or x=1.025×10
• −4
• [OH
• −
• ]=Cx=1.025×10
• −4
• ×0.05=5.125×10
• −6
• M
• [H
• +
• ]=
• 5.125×10
• −6
• 1×10
• −14
• =1.95×10
• −9
• M
• pH=−log[H
• +
• ]=−log(1.95×10
• −9
• )=8.71