“assigned” pH of 6.6 because of the amount of each buffer component added. The amount of buffer components added could be inaccurate because the scales used to measure the mass of the buffer components would fluctuate. This made it so I couldn’t get an exactly accurate measurement. The scales also only went out to three decimal places, while the calculated mass that was needed of each buffer component went out to 9 decimal places. This also accounts for a slight difference in the pH because of the inability to be 100% accurate. Since my measured pH was lower than the “assigned” pH more of the acidic buffer component was added than measured, or less of the basic buffer component was added than measured, or a combination of the two. 2. How did the predicted pHs which you calculated for HCl and NaOH added to water compare to those that you measured? What could account for any differences observed? (Be specific.) The calculated pH values for NaOH and HCl in water were quite close to the values that I measured. The predicted pH of NaOH added to water is 11.3, the measured pH is 11.0, and the percent error is -2.65 %. The predicted pH of HCl added to water is 2.7, the measured pH is 2.96, and the percent error is 9.63 %. The measured pH of NaOH is only off by -0.3 pH, and the measured pH of HCl is only off by 0.26 pH. I think that since the measured basic pH isn’t as high as predicted to be and the measured acidic pH isn’t as low as predicted to be that neither a full mL of NaOH or HCl was added to 50 mL of the buffer solution. I think that a full mL of each component didn’t get added because some of each was left behind in the
graduated cylinder that it was measured in. Each component was measured out to 1 mL precisely, so a small amount of each component must have stuck to the inside of the graduated cylinder because of the adhesion between the liquid molecules and the glass.