Name: ______________________________
Per: _____
Performance:
BIOCHEMISTRY LAB 2: QUALITATIVE ANALYSIS TESTING FOR CATIONS & ANIONS
BACKGROUND
Take a look at the lab report shown below.
What cations and anions do you see listed in this lab report? Cations and anions play very important
roles in health and medicine. Ions such as sodium, potassium, calcium, chloride, phosphate, and bicarbonate
are needed to maintain proper hydration and blood pH, and they are needed for the proper function of nerve
and muscle tissue. Abnormal levels of these ions in the body can have severe consequences leading to
cardiac and neuronal problems, and if not treated can even cause death.
When a doctor orders a chemistry panel (also known by a variety of other names such as Chem12,
Chem 7, SMA 20, SMAC, CMP, etc.) for a patient a sample of the patient’s blood is sent to a lab where a series
of tests are carried out to measure the presence and quantity of certain chemicals, some of which are ions.
Ever wondered what the lab technician does to find out what chemicals are in these blood samples?
Lab technicians perform a series of chemical reactions that give distinct results, such as color changes,
the formation of gases or insoluble precipitates, for each of the ions being tested. The results of a given
chemical reaction are specific to the presence or absence of one particular ion, and the expected results have
been tabulated using solutions containing the specific ion of interest (known as a standard). When the lab
technician performs a given test on the blood sample s/he records his or her observations of the results. By
comparing these observations to the expected outcomes, the lab technician can determine the presence or
absence of a given ion in the blood sample.
This type of analysis, where only the presence or absence of a particular substance (in this case ions) is
determined, is called qualitative analysis. A thorough clinical analysis however will move beyond simply
measuring the presence/absence of certain substances. It will include quantification which is called
quantitative analysis. Most of the blood work done these days involves quantification and then comparing it to
a certain standard. Values are then determined in range or out of range giving the clinitian an idea what’s going
on in a sick patient.
Name: ______________________________
Per: _____
Performance:
PRE-LABORATORY QUESTIONS
(1). Write the chemical symbol or formula for the following:
Sodium ion:
Potassium ion:
Calcium ion:
Chloride ion:
Phosphate ion:
Bicarbonate ion:
Sodium chloride:
Sodium bicarbonate:
Potassium phosphate:
Calcium bicarbonate:
Potassium bicarbonate:
Calcium phosphate:
Calcium Chloride:
Strontium nitrate:
Copper (II) Nitrate:
(2). There are different testing goals in chemistry, there is qualitative as well as quantitative analysis. What is
the difference between them?
(3). You detect the presence of calcium ions in a sample using the flame test. What additional test could you
do to confirm this finding?
(4). You are given a solution that is supposed to contain calcium phosphate. What tests can you perform to
confirm the presence of this calcium phosphate? Provide a brief procedure including any observations you are
likely to make.
(5) For which substances is the patient’s log on page 1 in or out of range?
Name: ______________________________
Per: _____
Performance:
PROCEDURE
The goal of this laboratory is to introduce you to the process of qualitative analysis by determining the
ionic composition of an unknown solution (imagine it is the serum from a patients blood sample). You will first
carry out a series of experiments on solutions containing a particular cation or anion (standard solutions) and
record your observations. Then you will repeat these experiments and record your observations on a solution
containing unknown ions (the unknown solution). You will then compare your observations for the unknown
with those obtained for the standard solutions and make a qualitative determination as to the ionic composition
of the unknown solution.
A. TESTS FOR CATIONS
A 1. Flame test for sodium, potassium, calcium, strontium, copper
 Obtain the standard NaCl, KCl, CaCl2 ,Cu (NO3)2 ,Sr (NO3)2 solutions (these are your known solutions).
Place the wire loop of the flame test wire into the vial with the NaCl solution and then into the flame.
Record the color produced by the Na+ ion. Repeat the test with the KCl solution. The color (pinklavender) of K+ does not last long, so look for it immediately. Record the color of the K+ ion. Repeat the
flame test with Ca2+. Record the color of the Ca2+ flame.
A 2. Oxalate test for calcium
 Place 5-6 drops of the standard CaCl2 solution in a plastic well (this is your known solution). Add 1-2
drops of ammonium oxalate solution, (NH4)2C2O4. Look for a cloudy, white solid (precipitate). If the
CaCl2 solution remains clear, transfer the solution by pipette to a ceramic plate well and heat gently on
the hot plate. Set the hot plate to its lowest setting. Look for a precipitate. The net equation for the
reaction is:
Ca2+ (aq) + C2O42- (aq) → CaC2O4 (s)
white precipitate indicates the presence of Ca2+
A 3 Test for ammonium ion, NH4+
 Place 5-6 drops of the standard NH4Cl solution in one well of a ceramic plate (this is your known
solution). Add 2 drops of sodium hydroxide (NaOH). You may notice the odor of ammonia. Place a
strip of moistened red litmus paper across the top of the well and set the plate on a hot plate to warm.
Set the hot plate to its lowest setting. The NH3 (g) given off will turn the red litmus paper blue. Record
the results.
NH4+ (aq)
+
OH- (aq)
→
NH3 (g)
+
H2O
Name: ______________________________
Per: _____
Performance:
B. TESTS FOR ANIONS
B 1. Silver nitrate test for chloride
 Place 5-6 drops of the known NaCl solution in a plastic well. Add 1 drop of AgNO3 and 1-2 drops of
nitric acid (HNO3). Caution: AgNO3 stains the skin. Any white solid that remains is AgCl (s) which
should not dissolve upon the addition of HNO3. Record the results.
Ag+ (aq) + Cl- (aq) → AgCl (s)
white precipitate remains after HNO3 is added
B 2. Ammonium molybdate test for phosphate
 Place 5-6 drops of the Na3PO4 solution in a well of the ceramic plate. Add 1-2 drops of HNO3. After the
solutions are warmed on a hot plate (adjust the hot plate setting to 2 or 3), add 2 drops of ammonium
molybdate solution, (NH4)2MoO4. The formation of a yellow precipitate indicates the presence of PO43-.
Record the results.
B 3. Carbon dioxide test for carbonate/bicarbonate
 Place 5-6 drops of the standard Na2CO3 solution in a plastic well. While carefully observing the solution,
add 1-2 drops of HCl. Watch for the evolution of bubbles of CO2 gas as you add the hydrochloric acid
(HCl). The gas bubbles are formed quickly, and may be overlooked. If gas bubbles were not observed,
add another 2-3 drops of HCl as you watch the solution. Record your results.
Na2CO3 (aq)
+
2 HCl (aq)
→ CO2 (g)
gas bubbles
+
H2O
+
2 NaCl (aq)
C. TESTING A SOLUTION FOR UNKNOWN CATIONS AND ANIONS
C 1. Write down the unknown sample number.
C 2. Repeat each of the tests (A1, A2, A3, B1, B2, and B3) for the unknown solution and write down
your observations. Repeat each test A1, A2, A3, B1, B2, and B3 as you did in parts A and B
but now you will be using the unknown solution.
 For example when performing the flame test place 8-10 drops of unknown solution into an empty well of
a plastic well plate. Place the wire loop into the solution and then into the flame. Record your
observations. Dip the wire loop in an HCl solution to remove any remaining residue when you are
finished.
C 3. Compare these observations to those that you obtained in sections A and B. Determine the
cation(s) and anion(s) present in your sample.
Name: ______________________________
Report Sheet
A. TESTS FOR CATIONS
Procedure
Cation tested
Observation
Sodium
Potassium
A 1. Flame test
Calcium
Strontium
Copper (II)
A 2. Oxalate test
Calcium
A3. Ammonium Test
Ammonium
B. TESTS FOR ANIONS
Procedure
Cation tested
B 1. Silver nitrate test
Chloride
B 2. Ammonium molybdate test
Phosphate
B 3. Carbon dioxide test
Carbonate
Observation
Per: _____
Performance:
Name: ______________________________
C. TESTING A SOLUTION FOR UNKNOWN CAT/ANIONS
Procedure
Flame test
Cation
tested
Sodium
Potassium
Calcium
Strontium
Copper (II)
Oxalate
test
Calcium
Silver
nitrate test
Chloride
Ammonium
molybdate
test
Phosphate
Carbon
dioxide test
Ammonium
test
Observation Sample #_____
Per: _____
TEST 2 SAMPLES
Observation Sample # _____
Carbonate
Ammonium
C3: Based on your observations above, complete the following chart:
Cations:
Anions:
Cations:
Anions:
Sample # ___ had the following:
Sample # ___ had the following:
Performance: