Buffer Solutions Lab

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Chemistry

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Dec 6, 2023

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PRE-LAB QUESTIONS 1. What would you estimate the pH of hydrochloric acid, a strong acid, to be? What is the pH of water? I’d estimate the pH of hydrochloric acid to be about 3. The pH of water is 7. 2. Use the Henderson-Hasselbalch equation to estimate the pH of a buffer solution that is composed of 20 mL of 10 M sodium formate and 20 mL of 1 M formic acid (Note: the pKa of formic acid is 3.75). Moles of sodium formate = (20*10*10^-3)= 0.2 moles Moles of formic acid (20*1*10^-3)= 0.02 moles pH= 3.75 + log 10 =3.75 + 1 = pH of 4.75 3. Look at Table 4 in the procedure portion of the experiment. Calculate the pH you would expect each of the buffer solutions (A, B, C, D, and E) to be using the Henderson- Hasselbalch equation, assuming that the solutions of acetic acid and sodium acetate are equimolar. Preparation of Buffer Solutions

A= 4.74+log n/5*10^-3 B= 4.74+log5 = 5.43 C= 4.74+ log 10= 5.74 D= 4.74-1 = 3.74 E= 4.74-0.69 = 4.05 EXPERIMENT 1: PREPARING A BUFFER Data Sheet Table 3: Sodium Acetate Data Sodium Acetate (g) Molarity of Sodium Acetate (Step 7) 4.0g 0.4876 Table 4: Buffer Solutions and pH Readings for Beakers A, B, C, D, and E Buffer mL of Acetic Acid mL of Sodium Acetate pH measured A 5 5 4.74 B 5 1 5.43 C 10 1 5.74 D 1 10 3.74 E 1 5 4.05 Post-Lab Questions 1. What are the calculated pH values for the buffers (A,B,C,D and E) that you measured in Table 4? Preparation of Buffer Solutions

A= 4.74+log n/5*10^-3 B= 4.74+log5 = 5.43 C= 4.74+ log 10= 5.74 D= 4.74-1 = 3.74 E= 4.74-0.69 = 4.05 4. Describe the process you used to calculate the molarity of your solution. Titration is used to determine the molarity of a solution. A conical flask with a known capacity is filled with the titrant, indicator, and titrant from the burette, one drop at a time. We switch off the burette's knob and record the burette reading once the color shift occurs and remains constant. This is the titration's finish point. Similarly, we do three titrations and determine the titrant’s average volume. Already, strength has been bestowed. Using the formula, then M1V1 = M2V2 we can determine the strength. 5. If you did not use different pipettes for the sodium acetate solution and the acetic acid solution describe all of the potential errors that could have occurred. The concentration of acetic acid would have grown if the two solutions were combined. Because acetic acid is a weak acid and does not dissociate or modify [H+], it has an impact on pH. Preparation of Buffer Solutions

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