Koby Cha
Chemistry
Lab#
Title: Flame Test for Cations
Aim: To determine the colours of the atomic emission spectra of several metallic cations by their
flame test
APPARATUS: Glass Rod, Containers, Bunsen Burner
REAGENTS: Sodium Sulphate, Potassium Nitrate, Calcium Nitrate, Barium Chloride,
Copper Sulphate
DIAGRAM
PROCEDURE:
A glass rod was dipped into the containers with the substance supplied.
The glass rod with the substance was then held in the bunsen burner flame.
Step one and two were repeated for the other substances.
RESULTS:
Compound
Color of flame
Sodium Sulphate
Orange
Potassium Nitrate
Light Purple
Calcium Nitrate
Orange-Red
Barium Chloride
Green
Copper Sulphate
Green
CALCULATIONS:
-h = 6.626 × 10-31 J•s (Planck's constant)
-c = 3.0 x 108 m/s (speed of light)
1. 590 nm (Sodium Sulphate, Orange )
E =(6.626 x 10^-34) (3.0 x 10^8)
590 × 10^-9
=3.37 x 10^-19 J
2. 405 nm (Potassium Nitrate , Lilac)
E =(6.626 × 10^-34) (3.0 × 10^8)
405 × 10^-9
=4.91 x 10^-19 J
3. 620 nm (Calcium Nitrate , Orange-Red)
E=(6.626 x 10^-34) (3.0 × 10^8)
620 × 10^-9
=3.21 x 10^- 19 J
4. 495 nm (Barium Chloride, Green)
E =(6.626 × 10^-34) (3.0 × 10^8)
495 × 10-9
=4.02 x 10^-19 J
5. 510 nm (Copper, Green)
E =(6.626 × 10^-34) (3.0 x 10^8)
510 x 10^-9
=3.90 x 10^-19 J
DISCUSSION:
We can use something called a flame test, where metal ions get their electrons excited when
they're exposed to heat. When electrons absorb energy, they are elevated to a higher energy level,
and when they return to their ground state, they emit that energy as light. The color we see when
light is emitted is being emitted at a specific wavelength, which is unique to the element.
When an element is excited and releases colored light, it does so at a unique wavelength. The
energy of those emitted photons determines the color of the flame. High-energy emissions emit
isotope blue or violet light while low-energy emissions emit isotope red, orange, or yellow light.
Each element has a unique electron configuration, thus resulting in different amounts of energy
released, which then results in unique colors of flame.
Sodium, for example, gives an orange flame, potassium gives a lilac flame and copper gives a
green flame.
Sodium, for instance, produces an orange flame; potassium, lilac; and copper, blue green. These
various colours enable us to use the flame test to identify metal ions.But it comes with its
limitations:
Subjectivity: The colors of flames can be hard to distinguish.
Inconsistency: Not all media will be compatible with each other, resulting in colors going into
another
Low sensitivity: May be unable to detect small concentrations
That being said, we need to be aware of these limitations, and the flame test should always be
seen as a qualitative technique, useful for differentiating between unknown elements but not to
measure precise concentrations of the elemental content. Some use it alone, but it is often used
with other analytical methods for greater accuracy
SOURCES OF ERROR:
-Samples being contaminated
-Misinterpretation of colours
CONCLUSION:
Flame tests help people deduce the energy of metal ions based on the color they produce when
brought to a flame. Accuracy is affected by contamination of reagents and color interference.
Despite its limitations, the test remains a useful tool for detecting
metal ions.
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