Chemistry
Lab - Acid-Base Titration
When an acid and a base are mixed together, a neutralization reaction occurs where the properties of the acid and
the base are destroyed.
+
-
According to Arrhenius, an acid has H ions in a water solution and a base has OH ions in a water solution. When
+
equal amounts of H ions and OH ions react, the product produced is water. Both the acidic and basic properties will
disappear.
A typical acid-base ionic equation is shown below:
+
-
+
-
+
-
H (aq) + Cl (aq) + Na (aq) + OH (aq)  H2O(l) + Na (aq)+ Cl (aq)
Hydrochloric Acid
Sodium Hydroxide
Water
Salt
+
-
The spectator ions are Na (aq) and Cl (aq). Omitting them from the equation leaves a net ionic equation:
+
-
H (aq) + OH (aq)
 H2O(l)
You will be doing a neutralization reaction between an acid and a base. Knowing the molarity of one of the chemical
and the volume used, you can determine the molarity (concentration) of the other chemical by using the following
mathematical equation:
(Molarity of the acid) x (volume of acid used) = (Molarity of the base) x (volume of base used)
M A • VA = MB • VB
This mathematical relationship is only true when the titration is at the end point (pH = 7).
Procedure:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
Fill the buret with base pass the zero mark. (Only do this for your first titration)
Drain the buret so the liquid level is right at the zero mark. (This removes any air from the tip and the valve)
Record the starting volume of the base buret.
At the front of the room there are burets that contain acid. You will get your acid from these burets.
Record the initial volume of the acid buret.
Add 10 mL of acid to a flask from the buret.
Record the final volume of the acid in the buret.
Add 10 mL of water to the flask.
Add 2 drops of indicator (phenolpthalein).
Now slowly add the base from the base buret, swirling the flask as it is being added.
Continue adding base slowly until ONE drop of the base changes the color of the flask from clear to pink
(reddish). This is the end-point where the pH = 7. It may be helpful to have a white piece of paper lying under
the flask, this will help to determine when the solution is changing colors.
Record the final volume of the base buret.
Dump out the flask, in the sink with the water running. Rinse out the flask.
Refill the burets or use them as they are, but record the new starting amount of the buret.
Next group member repeats steps 3-13.
FOR LAST BLOCK OF THE DAY ONLY - When ALL members of the group have done a titration, drain the base
buret into a beaker. Then fill the buret with distilled water and let it run through into the beaker.
Work on calculations.
Chemistry
Lab – Titration
Names: ___________________________
___________________________
___________________________
___________________________
Group #: ______ Block: _______
Data and Calculations
Molarity of ACID used: ________
Group Member # 1
Your initials: ______
Starting Volume of acid in buret ___________ mL
Final Volume of acid in buret ___________ mL
Starting Volume of base in buret _________ mL
Final Volume of base in buret
_________ mL
(VA)Volume of acid USED ___________ mL
Molarity of Base
___________ M
(VB) Volume of base USED
(SHOW WORK BELOW)
Group Member #2
Your initials: ______
Starting Volume of acid in buret ___________ mL
Final Volume of acid in buret ___________ mL
Starting Volume of base in buret _________ mL
Final Volume of base in buret
_________ mL
(VA)Volume of acid USED ___________ mL
Molarity of Base
___________ M
(VB) Volume of base USED
Your initials: ______
Starting Volume of acid in buret ___________ mL
Final Volume of acid in buret ___________ mL
Starting Volume of base in buret _________ mL
Final Volume of base in buret
_________ mL
(VA)Volume of acid USED ___________ mL
___________ M
(VB) Volume of base USED
_________ mL
(SHOW WORK BELOW)
Group Member # 4
Your initials: ______
Starting Volume of acid in buret ___________ mL
Final Volume of acid in buret ___________ mL
Starting Volume of base in buret _________ mL
Final Volume of base in buret
_________ mL
(VA)Volume of acid USED ___________ mL
Molarity of Base
_________ mL
(SHOW WORK BELOW)
Group Member # 3
Molarity of Base
_________ mL
___________ M
(VB) Volume of base USED
_________ mL
(SHOW WORK BELOW)
Using the molarities of base from all members, what is your average molarity of the base? _______ M
Titration Lab Supplement
1. In lab a student neutralizes HNO2 with Ca(OH)2
A. Write the total ionic equation for the reaction between HNO2 (aq) and Ca(OH)2 (aq). Make sure it is
balanced!
B. Write the net ionic equation for this reaction.
2. Fix all the problems that you find in this total ionic equation, circle any part that is wrong and then write what that
part should be.
Ca+ + 2 OH -(aq) + 2 H+ (aq) + Cl- (aq)
H2O + Ca+ (aq) + 2 Cl-
3. Show acetic acid (HC2H3O2), a weak acid when it is put into water.
4. Show strontium hydroxide Sr(OH)2, a weak base when it is put into water.
5. A 150 mL sample of KOH requires 1.2 L of 0.05M HCl to neutralize it. What is the concentration of the KOH?
(SHOW WORK)
6. How many milliliters of .75M LiOH would be required to neutralize 85.7 mL of HNO2? The molarity of the HNO2
is .28M. (SHOW WORK)
CHALLENGE PROBLEMS – everyone must try these!
7. Show the complete and total dissociation of H3PO4 when it is put into water.
8. How many grams of NaOH were used to make 1 Liter of a solution where 35.9 mL of it were required to
neutralize 23.5 mL of .25M HCl? (SHOW WORK) Hint – think about how molarity and grams can be related.