Title: Potentiometric Titration
Purpose: The purpose of this lab was to construct a titration curve by titrating Formic acid using a standardized sodium hydroxide (NaOH) and a pH meter through potentiometric titration. After the data for the rest of the class is collected, compare and contrast the equivalence points to see how the concentrations of the various acids affected the acids weakness and strength.
Methods:
Obtain 0.020 M of Formic Acid (HCCOOH). Calibrate the pH meter using the instructions for calibrating the pH meter in the appendix. After the calibration of the pH meter, 150 mL of Formic acid solution was dispensed into a clean dry beaker, and then 50 mL of the formic acid was transferred into a 250mL beaker.
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The size of (NaOH) was reduced to about 0.1 mL per intervals. A titration curve was made for 0.20 M of Formic Acid and results were shared in class. After the data has been collected from the rest of the class, compare and contrast the properties of various acids titrated with a strong base. Keep in mind that that the pH of the strong acid reacted with strong base will give a pH of about 7 and a weak acid with a strong base will give a pH higher then 7.
Data:
Table 1: Acids Studied in the Experiment
Acid Ka1 Ka2
Hydrochloric acid, HCl very large N/A
Acetic acid, CH3COOH 1.76E-5 N/A
Formic acid, HCOOH 1.77E-4 N/A
Maleic acid, HOOCCHCHCOOH 1.42E-2 8.57E-7
Acids with very large Ka values are very strong acids. Acids with very small Ka are very weak acids. Hydrochloric acid is very strong because of its very large ka value, and the rest of the acids are weak because of their small Ka values. Hydrochloric acid, acetic acid, and formic acid are all monoprotic. Maleic acid is diprotic because it has two acidic protons that leave it when it reacts with a base.
Table 2. Titration Data for various Acids
initial pH pH at ½ equivalence Volume at equivalence final pH
<ol>
<li value="0">010 M HCl 2.10 2.30 4.96 11.30
<li value="0">020 M HCl N/A N/A N/A N/A
<li value="0">030 M HCl N/A N/A N/A N/A
<li value="0">010 M CH3COOH N/A N/A N/A
The purpose of this semester long experiment was to determine an unknown organic acid. An organic acid is an organic compound with acidic properties. A base reacts with acids to form salts. Titrations are used to determine the concentration of unknown substances. The purpose of the KHP experiment was to determine the molarity of NaOH. HCl titrations are mainly to check technique and used to verify the molarity of NaOH solution. The hypothesis is that this acid is C4H3OCOOH.
mL cylinder to the beaker on the stir plate and empty it into the beaker. Place the pH probe in the beaker and record the pH in the data table. Drag the beaker to the red disposal bucket. Double-click the bottle of NaHCO3 to move it to the Stockroom counter. Repeat steps 5 and 6 for KNO3.
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