CHEMISTRY IN CONTEXT
TITRATION LAB, PAGE 1
NOVEMBER 16, 2006
NAME
Acid Base Titration
PRE-LAB DISCUSSION:
Titration Defined:
Titration is the addition of small amounts of a base to an acid to determine the point when the
base has neutralized the acid. If you do not add enough base, the solution will remain acidic, and
if you add too much base, the solution will be alkaline (or basic). Today, you will try to find the
end point of a titration with HCl and a base.
A tritration in conducted using a very accurate volumetric column called a buret. A buret adds
small drops of the base to the acid by turning the small knob at its tip. A buret may even be
turned to add a certain number of drops in a given time period.
Tummy Ache:
Heartburn and indigestion is often caused by overproduction of HCl or hydrochloric acid by the
stomach. The acid slowly dissolved the lining of your stomach and can sometimes lead to more
serious gastro-intestinal conditions if it is not treated. We often treat indigestion and heart burn
with antacid tablets (anti-acid tablets). The tablets are essentially a weak base that is being used
to neutralize a strong acid.
Today’s titration will simulate the addition of antacid to an artificial stomach (beaker of HCl).
We will try to determine which antacid is the strongest. The strongest antacid will be the one
that requires the least amount to neutralize the irritated stomach.
Some IMPORTANT SAFTEY REMINDERS:
1)
You will observe STANDARD PRECAUTIONS today.
2)
HCl is a caustic acid and should be treated with care. Exposure to the acid should be
treated with baking soda and then soap and water.
APPARATUS/MATERIALS:
mortar and pestle
various antacids
buret
buret clamp
funnel
10mL HCl
100mL graduated cylinder
2 600mL beakers
indicator (of your choice)
pH paper
large glass stirring rod
CHEMISTRY IN CONTEXT
TITRATION LAB, PAGE 2
NOVEMBER 16, 2006
NAME
PROCEDURE:
1)
Place the buret in the buret clamp so that a large beaker could fit underneath it.
2)
Use the graduated cylinder to measure 25mL of HCl into a 600mL beaker. Then,
RINSE the graduated cylinder out.
3)
Add 40 drops of your choice of indicator to the beaker with the acid. Swirl the
beaker, and place it underneath the buret.
4)
Select one of the following antacids:
a) Mylanta
b) Maalox
c) Tums
d) Rolaids
5)
If you select one of the first two in the list, following steps #6-13. If you select one of
the last two on the list, follow steps #14-21.
6)
Use the graduated cylinder to measure 10mL of antacid into an empty 600mL beaker.
Then, use HOT tap water to dilute the antacid to 300mL.
7)
Place a funnel into the top of your buret. Make sure that the stopcock on the buret is
turned perpendicular to the buret so that’s its NOT OPEN.
8)
Carefully and SLOWLY (to prevent overflow) fill your buret to the highest mark on
the top.
9)
Dip one small piece of pH paper into the acid beaker and compare the color it
changes to the sides of the pH paper container to determine the pH of your solution.
Record this number ALONG WITH the color that the indicator appears in the acid
beaker.
10)
Turn your stopcock on your buret and begin adding antacid solution to your acid
beaker. EVERY 25mL, check the pH of the acid beaker using a small strip of pH
paper AND record the color of the indicator in the beaker.
11)
After your buret empties, check the pH of the acid beaker using a small strip of pH
paper AND record the color of the indicator in the beaker. REFILL your buret with
antacid solution and repeat step 10.
12)
Continue steps #10-11 until your have emptied your antacid beaker.
13)
Clean up all materials by disposing them down the sink. Use the EXTRA LONG test
tube brush to clean out your burets.
14)
Acquire TWO antacids tablets and use your mortar and pestle to grind them up to a
FINE powder. Add the powder to an empty 600mL beaker. Dilute the tablets with
HOT water up to 300mL. Use your stirring rod.
15)
Place a funnel into the top of your buret. Make sure that the stopcock on the buret is
turned perpendicular to the buret so that’s its NOT OPEN.
16)
Carefully and SLOWLY (to prevent overflow) fill your buret to the highest mark on
the top.
CHEMISTRY IN CONTEXT
TITRATION LAB, PAGE 3
NOVEMBER 16, 2006
17)
18)
19)
20)
21)
NAME
Dip one small piece of pH paper into the acid beaker and compare the color it
changes to the sides of the pH paper container to determine the pH of your solution.
Record this number ALONG WITH the color that the indicator appears in the acid
beaker.
Turn your stopcock on your buret and begin adding antacid solution to your acid
beaker. EVERY 25mL, check the pH of the acid beaker using a small strip of pH
paper AND record the color of the indicator in the beaker.
After your buret empties, check the pH of the acid beaker using a small strip of pH
paper AND record the color of the indicator in the beaker. REFILL your buret with
antacid solution and repeat step 10.
Continue steps #10-11 until your have emptied your antacid beaker.
Clean up all materials by disposing them down the sink. Use the EXTRA LONG test
tube brush to clean out your burets.
DATA/OBSERVATIONS:
Volume
Titrated
(mL)
25
50
75
100
125
150
175
200
225
250
275
300
pH
(paper)
Indicator
Color
(beaker)
CHEMISTRY IN CONTEXT
TITRATION LAB, PAGE 2
NOVEMBER 16, 2006
NAME
ANALYSIS:
1)
Which indicator did you use? Use the Internet OR your old lab to determine the colors
that it will turn in the presence of the following:
a)
strong acid
b)
weak acid
c)
neutral
d)
weak base
e)
strong base
2)
Use a piece of graph paper to graph the pH of your solution as a function of titrated
volume. So, pH is on the Y axis and titrated volume is on the X axis.
Use the attached graph paper….
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Acid-Base Titration - The Lexington School