Make the following buffer and measure its pH: 100.0 mL 3.0 M (30 times 10^-1) HC
ID: 511906 • Letter: M
Question
Make the following buffer and measure its pH: 100.0 mL 3.0 M (30 times 10^-1) HC_3H_5O_3(aq) 100.0 mL 7.0 M (70 times 10^-1) NaC_3H_5O_3(aq) When 50.0 times 10^-3 mol HCl are added to the solution, the pH = 4.21. When 50.0 times 10^-3 mol NaOH are added, the pH = 4.23. Compare the change in pH of this solution with that of solution 2 from Table 13.1. Which one is the better buffer? What is the only difference between these two solutions? You must include all data you collected or you analyzed, all your calculations, all tables, from Parts 1 and 2 in your report.Explanation / Answer
PH = PKa + log[Salt]/[Acid]
no of moles of CH3COOH = molarity * volume in L
= 3*0.1 = 0.3moles
no of moles of CH3COONa = molarity * volume in L
= 7 * 0.1 = 0.7 moles
PH = PKa + log[CH3COONa]/[CH3COONa]
= 4.75 + log0.7/0.3
= 4.75 + 0.3679 = 5.1179
no of moles of HCl = 0.05moles
no of moles of CH3COOH = 0.3+0.05 = 0.35 moles
no of moles of CH3COONa = 0.7-0.05 = 0.65 moles
PH = 4.75 + log0.65/0.35
= 4.75 + 0.2688 = 5.0188
no of moles of NaOH = 0.05 moles
no of moles of CH3COOH = 0.3-0.05 = 0.25 moles
no of moles of CH3COONa = 0.7+0.05 = 0.75 moles
PH = 4.75 + log0.75/0.25
= 4.75 + 0.4771 = 5.23
second buffer solution PH difference is less . so it is good buffer solution.
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