In our next lab, we are going to use our titration that involves our unknown solid acid and our base, which is NaOH. We will titrate our unknown solid acid with NaOH and each 0.5 increments and measure their pH by using the Venier device. Then, using our data, we will determine our equivalence point. From Exploring Chemical Analysis, an equivalence point is the titration of the quantity sufficient for stoichiometirc reaction with the analyte. The Venier device will help us measure the solution’s pH. After getting our required measurements, we will then calculate our molar concentration of HA (mol/L), our unknown acid, our molar mass, and our Ka but since our measurement volumes is in milliliters, we will have to convert the volume into liters.
Materials 0.1 M sodium hydroxide solution (NaOH)
250 mL volumetric flask
250 mL beaker
Venier device with pH probe
Magnetic stirring plate
Unknown weak monoprotic acid or diprotic acid
To start with our experiment, we first gather our sample of the unknown acid. We measured the unknown acid using the scale and our unknown acid mass reads 1.513g. We recorded our mass so we will use the mass for our calculations. Then, 75 mL of distilled water is pour into the beaker so we can put the unknown acid into the beaker and mix it until the acid is completely dissolve. We then take 25 mL aliquot of the acid solution with a pipette and place it in the beaker plus including a magnetic stirring bar. The magnetic stirring bar will help us with our solution. Then, we poured the NaOH into the buret so we will be ready for titration. We first measure our pH of our solution so will get our initial pH but we first wait for one minute to get our reading. After one minute, our initial pH is 4.12pH. We then will add the NaOH into the volumetric flask and for our volume; each increments will be 0.5mL.
Table 1 Table 2 mL of .1M NaOH added | pH of unkown acid | 0 | 4.12 | 0.5 | 4.47 | 0.9 | 4.68 | 1.4 | 4.92 | 1.9 | 5.09 | 2.4 | 5.25 | 2.9 | 5.45 | 3.4 | 5.71 | 3.9 | 6.08 | 4 | 6.14 | 4.1 | 6.38 | 4.3 | 6.71 | 4.4 | 7.13 | 4.5 | 10.07 | 4.7 | 11.17 | 4.8 | 11.48 | 4.9 | 11.68 | 5 | 11.7 | mL of .1M