Question

F. pH of Buffer after the addition of the Strong Base 1. Calculate the expected pH of this solution. 50.0 mL buffer + 2.0mLION NAOH pH 2. Measured pH of this solution. pH 4.59 3. What is the percent error between the calculated and measured value? What are some of the possible sources of this error? % error

pH of Buffer after the addition of the Strong Base: ix. Measure out 50.0 ml the buffer in part D and 2.0 mL of 1.0 M NaOH into a clean beaker. x Rinse the pH probe with DI H20 and place it into the solution in the beaker ensuring that the tip is completely immersed. xiAfter the pH value on the display has stabilized, record this value on the provided data sheet. xit. Remove the pH probe, rinse it, and place it in the waste beaker until you need it again to ensure that the electrode remains hydrated. Empty the solution and the remaining buffer solution from Part D into the waste beaker

D. pH of a Buffer Solution after addition of a Strong acid or a strong base. Preparation of a buffer solution: Buffer solution #3 PH=4.52 X Measure out 50.0 ml 1.0 M CH,COOH and 50.0 mL of 1.0 M NaCH,COO into a beaker. X. Rinse the pH probe with DIH,O and place it into the solution in the beaker ensuring that the tip is completely immersed. m. After the pH value on the display has stabilized, record this value on the provided data sheet. J. Remove the pH probe, rinse it, and place it in the waste beaker until you need it again to ensure that the electrode remains hydrated.

Answer 1

F) 50 ml buffer contains 25 ml CH3COOH,25 ml CH3COONa.

No of mol of CH3COOH = 25*1 = 25 mmol

No of mol of NaOH = 25*1 = 25 mmol

after addition of NaOH,

pH of acidic buffer = pka + log(CH3COONa+NaOH/CH3COOH-NaOH)

pka of CH3COOH = 4.74

No of mol of NaOH added = 2*1 = 2 mmol

pH = 4.74+log((25+2)/(25-2))

pH = 4.81

Theoretical pH = 4.81

2) Measured (Experimental) pH = 4.59

    Theoretical pH = 4.81

%error = (Theoretical- Experimental)/Theoretical*100

        = (4.81-4.59)/4.81*100

        = 4.57%