3. Theoretical pH of solutions and deionized water after the addition of strong
ID: 504214 • Letter: 3
Question
3. Theoretical pH of solutions and deionized water after the addition of strong acid and strong base in Part II of the experiment.
1. Concentrations of acetic acid and sodium acetate in the prepared buffer solutions in Part I as noted in the table in the lab handout
The acetic acid and sodium acetate solutions will have concentrations of 0.50 M.
Table 2: pH of Buffer Solutions & DI Water After Addition of Strong Acid or Strong Base Solution Theoretical pH Theoretical pH Measured pH Measured pH After Acid After Addition After Base After Addition of Acid Addition Addition of Base Ai N/A N/A B1 N/A N/A Wi N/A N/A A2 N/A N/A N/A C2 N/A W2 N/A N/AExplanation / Answer
Concentration of stock solution of acetic acid = 0.5M
Concentration of stock solution of sodium acetate = 0.5 M
Calculate [acetic acid] in buffer solution A = 25mL * 0.5/50mL = 0.25 M
Calculate [acetic acid] in buffer solution B = 45mL 0.5/50mL = 0.45 M
Calculate [acetic acid] in buffer solution C = 5mL * 0.5M/50mL = 0.05 M
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Calculated [acetate] in buffer solution A = 0.25 M
Calculated [acetate] in buffer solution B = 0.05 M
Calculated [acetate] in buffer solution C = 0.45 M
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Theoretical pH of buffer solution A : pH = pKa +log[acetate/acetic acid]
= 4.74 + log[0.25/0.25]
= 4.74
Theoretical pH of buffer solution B : pH = pKa +log[acetate/acetic acid]
= 4.74 + log[0.05/0.45]
= 3.78
Theoretical pH of buffer solution C : pH = pKa +log[acetate/acetic acid]
= 4.74 + log[0.45/0.05]
= 5.69
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