Question

Titration 1: weak acid (CH₃COOH) w/ strong base (NaOH)

Titration 2: strong acid (HCl) w/ strong base (NaOH)

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Concerning the above two titrations, answering the following questions:

1.) Calculate the theoretical equivalence point in terms of NaOH added for each of the titrations. Assume the concentration of acid is 0.81 M and the concentration of base is 0.51 M.

2.) Which equation can be used to find the pH of a buffer? Calculate the pH of a buffer containing 0.20 M CH₃COOH and 0.20 M CH₃COONa. What is the pH after adding 10.0 mL of 0.10 M HCl to 65.0 mL of the buffer?

3.) What volume of 0.8000 M NaOH partially neutralizes 25.00 mL of 0.1 M solution of a monoprotic acid?

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(Thanks so much in advance!)

Answer 1

2)

pH = pKa + log [salt / acid]

     = pKa + log [CH3COONa / CH3COOH]

pH = 4.74 + log [0.20 / 0.20]

pH = 4.74

after adding HCl

millimoles of CH3COOH = 65 x 0.20 = 13

millimoles of CH3COONa = 65 x 0.2 = 13

millimoles of HCl added = 10 x 0.1 = 1

pH = pKa + log [salt - C / acid + C]

     = 4.74 + log [13 - 1 / 13 + 1]

pH = 4.67

3)

At neutralization point :

millimoles of acid = millimoles of base

25 x 0.1 = 0.8 x V

V = 3.125

volume of NaOH = 3.125 mL