Elements, Compounds, and Mixtures Lab
Taylor Morrison
Partners: Hannah Austin, Sarah Austin
Date: 10/25/10
Purpose:
The purpose of this lab is to identify a set of flame test color standards for selected
metal ions, to relate colors of a flame test to the behavior of excited electrons in a
metal atom, and identify an unknown metal ion by a flame test.
***Hypothesis:
1.
Materials Needed:
1.0 M HCl Solution, K2SO4 Solution, NaCl Solution, Cu (NO3)2 Solution, CaCl2
Solution, LiCl Solution, Unknown Solution, 250mL Beaker, Flame Test Wire,
Diffraction Grating, Bunsen burner, Plastic Test Plate
Procedure:
1. Label a beaker Waste. Clean and dry a glass plate thoroughly. Put five drops of
1.0 M HCl on the clean plate. To clean the test wire, dip it in the HCl and hold it
on the colorless flame of the Bunsen burner. Repeat this until there is no color
from the wire on the flame. After this, rinse the plate with distilled water and
collect the rinse water in the Waste beaker.
2. On one side of the plate, put two drops of each metal solution in a row. Across
from the metal ion solutions, put a row of 1.0 M HCl drops on the plate. The wire
will need to be cleaned thoroughly between each of test solution. This will avoid
contamination from the previous test.
3. Dip the test wire in the SrCl2 Solution and hold it in the burner’s flame. Observe
the flame’s color and record it in the data table. Repeat the procedure, but while
using the diffraction grating to view the results. Record the wavelengths you see in
from the flame. Perform the tests three times each. Clean the wire with HCl again,
as you did in Step 2.
4. Repeat the Step 3 using the remaining solutions on the plate, and perform each
test three times. Record each flame’s color and their wavelengths that were
observed using the diffraction grating for each solution tested. Clean the wire
thoroughly and rinse the plate with distilled water into the waste beaker after the
solutions are tested.
5. Use the unknown metal solution in a flame test, using the previous steps.
Safety:
Always be wearing safety goggles and an apron, do not wear sandals, tie long hair
back, know the location of the fire extinguisher and safety blanket, always watch
the Bunsen burner when being used, and clean all equipment after use.
Observations:
Metal Compound Solution
SrCl2
K2SO4
CaCl2
NaCl
*LiCl
Cu (NO3)2
*Unknown
Observations
Pink sparks appear when cleaning
Very bright and glowing
Large orange and yellow flame
Very bright flame
∙Red/Orange-colored flame
∙When cleaning, there is a slight pink color
∙Takes a long time to clean
Blue-Green Flame
∙Red/Orange colored flame
∙Slight pink color when cleaning
∙Takes a long time to clean
*These are the same compound
Questions:
Q1: Why is it important to clean the test wire carefully between flame tests?
A1: It is important to clean the test wire carefully between flame tests because the
chemicals from a previous test will contaminate the current test if the wire is not
carefully cleaned.
Q2: Why do we see colors when the solutions are put in the flame? (Explain in
terms of what the electrons are doing)
***A2: We see colors when the solutions are put in the flame because the
electrons are
Q3: Why do different solutions give off different colors in the flame test?
Example: Why does the copper solution give off a blue flame while the sodium
gives off a yellow flame?
What accounts for the difference in colors?
***A3: Different solutions give off different colors in the flame test because
***Conclusion:
.
What I learned:
I learned that by testing an unknown metal ion on a flame, you can determine what
kind of metal ion it is by its flame. All metal ions vary, even when a flame test is
used.