the
process of determining
the molarity of an acid or
base by using an acid-base
reaction where one
reactant is of known
molarity.
Get your lab book and copy the
lab.
Title: Acid/Base Titration
Purpose: The purpose of this lab is to practice safe lab
technique, to expand our understanding of the acid/base
chemical reaction, and to gain experience in the use of
indicators.
Materials:
250 mL flask
50 mL beaker for 1.0 M HCl (hydrochloric acid)
50 mL beaker to measure water
2 eye droppers
water supply
phenolphthalein indicator
unknown concentration NaOH (sodium hydroxide) solution
Procedure:
1. Place 20 mL of water in a clean 250 mL flask.
2. Place 1 mL of 1.0 M HCl in the flask.
3. Place 5 drops of phenolphthalein indicator in the flask
and swirl.
4. Begin adding drops, one at a time of Unknown
concentration NaOH to the flask. Be sure and COUNT
the number of drops that you add. You will be looking for a
COLOR CHANGE. SWIRL THE FLASK EACH TIME YOU
ADD A DROP.
5. When the color change is stable, stop adding drops.
6. Perform steps #1 - #5 two more times.
7. Average your results.
8. Calculate the molarity of the unknown.
9. Calculate the percentage error of your results.
Data:
Volume of 1.0 M HCl = 1 mL
Number of drops of NaOH needed to reach the endpoint =______
Volume of 1.0 M HCl = 1 mL
Number of drops of NaOH needed to reach the endpoint =______
Volume of 1.0 M HCl = 1 mL
Number of drops of NaOH needed to reach the endpoint =______
Average number of drops = _____________
Calculations:
1. Write the balanced equation for the reaction and determine
the mole ratio.
NaOH + HCl  _______ + _______
2. Calculate the average number of mL of NaOH needed to
reach the endpoint based on 20 drops = 1.0 mL. (circle your
answer)
3. Calculate the molarity of the unknown NaOH solution using
Ma*Va = Mb*Vb. (circle your answer)
4. Calculate the percentage error of your results using the
provided expression. (circle your answer).
Tell what you learned during the lab and provide any
explanations of what errors may have occurred.
Calculations:
4. Calculate the percentage error of your results using the
provided expression. (circle your answer).
Accepted Value
% error
=
-
Experimental Value
Accepted Value
x
Tell what you learned during the lab and provide any
explanations of what errors may have occurred.
100