UNKNOWN ACID AND BASE TITRATION
The purpose of this experiment was that we explored the use of titration by adding small quantities of base to an acid and recording the rise of the pH on a graph so we can see the equivalence point. In this lab we used a strong acid and a strong base to perform the acid base titration. Strong acids and bases are known to dissociate in water completely. Some of the major findings in this lab were that only a small amount of base can result in a large change in the pH.
Step 1, Obtain acid, in a 100 ml Erlenmeyer flask add 35 ml of .2M HCl solution. Step 2, add an indicator to the acid, select the flask and add 2 drops of phenolphthalein indicator. Step 3, Fill buret with NaOH, obtain a 50 ml buret and fill with .2M NaOH solution.Step 4, Titrate NaOH into HCl until end point, record initial buret volume and add NaOH (quickly at first then slowly) until the HCl solution turns pink and record the final buret volume of NaOH in buret. Step 5, repeat steps 1-4 using pH meters, add a pH meter to the acid solution. Record several points of pH and NaOH added (especially near equivalence point) to be use later to prepare a titration curve.
Observations and Results
Solution | pH |
0.1 M HCl | .70 |
0.1 M NaOH | 13.30 |
Volume of 0.1 M NaOH at equivalence point: 35mL
pH at equivalence point: 11.45
Molarity of the Unknown Acid A (HCl):
2.0 x 10-4
In this lab, we found out that water self ionizes itself into hydrogen ion and hydroxide ion naturally to a very small extent. An indicator, in an acid base reaction, is a substance whose color changes over a particular pH range. Phenolphthalein is an example of an indicator which changes from colorless to pink as pH goes from 8 to 10. We plotted the pH against the amount of base added producing a titration curve. The steepest point on the curve occurs at the equivalence point, when the acid is...