Acid base Titration
Problem: How can the amount of acid in an unknown solution be determined?
Materials:
125mL Erlenmeyer flask
100mL graduated cylinder
Buret
Ring stand
Buret clamp
Safety goggles
NaOH
HCl
phenolpthalein
distilled water
Pre lab Questions:
1. If 24.3 mL of 0.085M NaOH solution are needed to completely neutralize 15.5 mL of an
unknown acid, what is the concentration of the acid solution?
2. What is the H+ in each of the following acid solutions?
a) 0.004 M HNO3?
b) 1.33 M HClO4?
c) 12MHI
Procedure
1. Obtain a sample of unknown acid as directed by your teacher. Measure approximately
10mL of the acid solution into a clean graduated cylinder. Record the exact volume, and
then place the acid in a clean 150-mL Erlenmeyer flask.
2. To the acid solution add six to eight drops of phenolphthalein indicator. Swirl to mix.
Note: the solution should be colorless at this point.
3. Place the flask containing the acid under the tip of the buret. It maybe helpful in detecting
the end point to place the flask on a piece of white paper.
4. Open the stopcock and allow the NaOH to flow slowly into the acid. As the NaOH drips
into the acid, swirl the flask completely mix the acid and base together. Continue
dripping the NaOH into the flask until the first persistent sign of pink appears.
5. Note and record the final volume of the base in the buret.
6. Repeat the titration with another 10.0mL of the same acid. Repeat the titration a third
time. Each time be careful to record the initial volume and the final volume of the KOH
in the buret.
Analysis and Conclusions
1. For each of the three titrations, determine the number of milliliters of NaOH required to reach the
end point
2.
Calculate the molarity of an unknown acid in each of the three samples
3.
Determine the average molarity of the unknown acid. Report your average answer to three
significant figures.
4.
a)
What effect should each of the following on the molarity of your acid solution?
rather than the desired light pink color, a bright magenta color marked the endpoint of the titration
b) Ten drops of phenolphthalein, rather than 6-8 were used in the titration
c)
The flask was not swirled during the titration, and the experiment was stopped at the first sign of
pink.
5.
a)
b)
c)
d)
Using chemical resources, identify the primary acid found in each of the following:
aspirin
vinegar
milk
fruit juices
Something Extra
Repeat this experiment to compare the amount of acid present in lemon juice, apple juice, orange juice or
grapefruit juice.( 10pts)
Conclusion: (5pts)
Rubric for the Activity: Acid base Titration
Parts of the Lab
Report
Introduction
Problem/
objectives
Materials
Procedure
Data/table
Pre lab Questions
Analysis
Conclusion
Possible points
3pts
Clearly stated objectives
( 3pts)
Complete (2pts)
Complete (3pts)
Complete with proper labels
(3 pts)
1.) 3pts
2.)
a) 2pts
b) 2pts
c) 2pts
1) 3 points
2) 3points
3) 2points
4)
a) 3 points
b) 3 points
c) 3points
5pts
With clear calculations
( 10 pts)
Something Extra
Neatness and
creativity of lab
report(includes
pictures of the
experiment)
Organization in
performing the
activity
Total
5 points
Participation of members /
Follow procedures and
clean working area
5 points
65 pts
Points Earned
Deductions
-.5 for unclear objective
-1 incomplete materials
-1 incomplete procedure
-1 without label
-1 unclear answer
-1 without solution
-.5without unit
-.5 without units
-1 without solution
-1 answer not in 3 significant
digits
- 1 unclear explanation
-.5 every answer without unit
-3 without showing
calculations for solving the
unknown concentration
-1 ( every missing part of
the lab-report)
-1 not presentable work
-1 no creativity
-1 messy working area
-1 always asking questions
to the teacher without
discussing it first with the
group
Common Ion Handout
Cations
+1
ammonium
copper(I) or cuprous
hydrogen
hydronium
lithium
potassium
rubidium
silver
sodium
Anions
-1
NH4+
Cu+
H+
H3O+
Li+
K+
Rb+
Ag+
Na+
2+
barium
Ba2+
cadmium
Cd2+
calcium
Ca2+
chromium(II) or chromous Cr2+
cobalt(II) or cobaltous
Co2+
Copper (II) or cupric
Cu2+
Iron (II) or ferrous
Fe2+
Lead(II) or plumbous
Pb2+
Magnesium
Mg2+
Manganese
Mn2+
Mercury (I) or mercurous
Hg2+
Mercury (II) or mercuric
Hg2+
Nickel
Ni2+
Strontium
Sr2+
Tin(II) or stannous
Sn 2+
Zinc
Zn2+
acetate
bicarbonate
bromide
chlorate
Chloride
Chlorite
cyanide
fluoride
hydride
hydroxide
hypochlorite
Iodide
Nitrate
Nitrite
Perchlorate
Permanganate
Thiocyanate
C2H3O2HCO3BrClO3ClClO2CNFHOHClOINO3NO2ClO4MnO4SCN-
2carbonate
chromate
dichromate
oxide
peroxide
selenide
sulfate
sulfide
sulfite
Thiosulfite
CO32CrO42Cr2O72O2O22Se2SO42S2SO32S2O32-
3+
aluminum
Chromium(III)
Iron(III) or ferric
Al3+
Cr3+
Fe3+
3nitride
phosphate
phosphate
N3PO43PO33-