Qualitative Analysis of Household Compounds
Sue Magrames and Matt Spreadbury-Oak Forest High School
1-708-687-0500 ext. 3712
Goal: To use simple chemical and physical tests to correctly identify seven white solid
compounds commonly found in the home. The solids will be chosen from the
following list:
Compounds used as unknowns Source
sodium chloride
table salt (uniodized))
sodium bicarbonate
baking soda
sodium hydroxide
drain opener (lye)
calcium carbonate
chalk
calcium sulfate
plaster of paris
starch
cornstarch
fructose
fruit sugar
sucrose
table sugar
magnesium sulfate
Epsom salts
Test reagents
phenolphthalein extracted from laxative tablets
iodine (tincture)
vinegar
distilled or deionized water
CuSO4-NaOH-Na2CO3 (Clinitest urine sugar test tablets)
Na2CO3 (washing soda)
Equipment provided
spot plate or well plate
wash bottle w/distilled water
conductivity tester (9v LED)
Quantity provided
about 3 mL
about 3 mL
about 10 mL
about 200 mL
1 tablet, broken
about 2 grams
glass rod or toothpicks for stirring
scoopula or spatula
dropper
STUDENTS MUST PROVIDE THEIR OWN SAFETY GLASSES!
General rules for this event:
1. Students will work as individuals.
2. Students must wear safety glasses and follow all standard safety practices. Taste-testing is
specifically prohibited.
3. Each student will receive about 3 grams of each unknown and the listed quantities of the
test reagents. These will not be refilled.
4. Each student may bring in one 4x6" note card with prepared notes/procedures. No other
notes or references are allowed. Calculators are neither needed nor permitted.
Score will be the number of unknowns correctly identified. Time will be used as a tie-breaker.
Background information
An article in the Journal of Chemical Education (Qualititative Analysis of Eleven Household
Compounds, Solomon, JChEd 68:328, April 1991) provides the basis for this experiment (but
a number of alterations have been made). Analytical tests include solubility in water, iodine test
for starch, acid test for carbonate, precipitation reactions, copper(II) reduction of
monosaccharides, phenolphthalein for base.
Significant changes from the cited procedure are:
1. Students will not have to prepare any reagents. All will be in ready-to-use form.
2. Students will use spot plates or well plates for testing.
3. Conductivity testers are used for the final test to distinguish salt from sugar.
4. The test for MgSO4 is changed from that in the above Journal article. Addition of
Na2CO3 produces insoluble MgCO3. This replaces formation of Mg(OH)2 by addition of
NaOH.
5. Students may modify the procedure if desired, but must follow usual safety practices
and use only the materials provided.
General procedure:
1. Test solid for solubility. Use several drops of water and a very small sample of solid.
2. Iodine test for starch: Add 1 drop of tincture of iodine to any insoluble sample in water.
Dark blue/black color indicates presence of starch.
4. Phenolphthalein test for NaOH: Add 1 drop phenolphalein to the sample solution. Bright
pink/red color is positive for NaOH. [Lighter pink color may be observed with NaHCO3.]
5. Sodium carbonate test for MgSO4: Add a few grains of Na2CO3 to the sample solution.
White precipitate is positive for magnesium sulfate. (This is a change from the JchEd
article--solutions of NaOH will not be provided.)
6. Vinegar test for NaHCO3 and CaCO3: Combine a few drops of vinegar with a small amount
of unknown. The evolution of CO2 indicates the presence of the carbonate or bicarbonate.
7. CuSO4 test for reducing sugar: Add about ¼ of a test tablet to the sample solution. A
red/yellow color indicates the reduction of Cu2+ by fructose.
8. Conductivity test for NaCl: Put a small amount of sample solution in a well and test. (NaCl
is an electrolyte.)
Analytical Scheme
NaCl, NaHCO3, CaSO4, NaOH, MgSO4, CaCO3, Cornstarch, Sucrose, Fructose
Water
Insoluble
CaSO4, Cornstarch, CaCO3
Iodine
Soluble
NaCl, NaHCO3, NaOH, MgSO4, Sucrose, Fructose
Phenolphthalein
Brown
Blue
CaSO4,
Cornstarch
CaCO3
Vinegar
Bubbles
CaCO3
Colorless
NaCl, MgSO4,
Sucrose, Fructose
Na2CO3
No change
CaSO4
Bubbles
NaHCO3
No reaction
NaCl, Sucrose, Fructose
CuSO4 tabs
Red/yellow ppt.
Fructose
Electrolyte
NaCl
White ppt.
MgSO4
No reaction
NaCl, Sucrose
Conductivity
Nonelectrolyte
Sucrose
Pink
NaOH (dark)
NaHCO3 (light)
Vinegar
None
NaOH
Qualitative Analysis
Name_____________________________________
School____________________________________
Session__________
Time_____________
***SET NUMBER_________
***OMISSION OF SET NUMBER RESULTS IN DISQUALIFICATION***
Match the numbered unknowns with the lettered compounds listed at right. Write the correct
letter for each sample:
1. __________
A. calcium carbonate
2. __________
B. calcium sulfate
3. __________
C. fructose
4. __________
D. magnesium sulfate
5. __________
E. sodium bicarbonate
6. __________
F. sodium chloride
7. __________
G. sodium hydroxide
H. starch
I. sucrose
Number correct____________
Place__________