M&M Lab
a.k.a. Empirical and Molecular Formulas Lab
Purpose:
To calculate the percent composition of each “element” and determine the empirical and molecular
formulas of the “compound.”
Introduction:
A compound has been chemically decomposed into its component elements. Each M&M represents one
mole of a particular type of “element.” Each color represents a different “element” and has its own
symbol and atomic mass, given in the chart below.
M&M’s
Color
Red
Orange
Yellow
Green
Blue
Brown
Symbol
R
Or
Y
G
Bl
Bn
Atomic Mass (g/mol)
1
2
3
4
5
6
You must show all work to receive credit!
Procedure:
1. Count each color of “element” and fill out the chart below. Each M&M represents one mole of the
“element.”
“Element”
Number of Moles
Present
Total Mass of “Element”
Present (g)
Number of “Atoms” Present
R
Or
Y
G
Bl
Bn
Empirical and Molecular Formulas Lab
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2. Write the empirical formula and calculate the empirical mass of your “compound.”
Empirical Formula:
__________________________
Empirical Mass: ______________ g/mol
3. Calculate the percent composition for each “element” in your “compound.”
“Element”
% Composition
R
Or
Y
G
Bl
Bn
Show work here:
4. Another lab found, through special tests, that the molecular mass is 3 times that of the empirical
mass. Write the molecular formula of your “compound” and calculate its molecular mass.
Molecular Formula: __________________________
Molecular Mass: ______________ g/mol
5. Another compound was found to be 3.3% Or, 25.0% Y, 13.3% G, and 58.3% Bl. Determine the
empirical formula and empirical mass.
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6. Another compound was found to be 5.5% R, 21.8% Y, 18.2% Bl and 54.5% Bn. Determine the
empirical formula, the empirical mass and the molecular formula if the molecular mass is 275
g/mol.
Empirical and Molecular Formulas Lab
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