Name
Date
Pd
Chemistry – Unit 4 Worksheet 3a
Use the following information about the masses of elements in each pair of compounds to help you
suggest formulas that account for these ratios.
1. Compounds of carbon and oxygen
Atoms of O are heavier than C atoms
by the ratio in compound A.
A
Compound A: 57.1 g O / 42.9 g C
Compound B: 72.7 g O and 27.3 C
a. Determine the value of the ratio
A ____
B _____
mass O
in each compound.
mass C
(assume the smallest ratio is a 1:1 ratio)
Mass of C:
B
Mass of O:
Mass of C:
Mass of O:
b. How does the mass ratio 
for compound B compare to that in
compound A?
c. Sketch particle diagrams for the compounds of A and B that account for these mass ratios. Write
the formula for the compound in each diagram.
2. Compounds of copper and oxygen
Atoms of Cu are heavier than O atoms
by the ratio in compound A.
A
Compound A: 79.9 g Cu / 20.1 g O
Compound B: 88.8 g Cu / 11.2 g O
a. Determine the value of the ratio mass Cu in each compound.
A ____
mass O
B _____ (assume the smallest ratio is a 1:1 ratio)
Mass of Cu:
B
Mass of O:
Mass of Cu:
Mass of O:
 compound B compare to that in
b. How does the mass ratio for
compound A?
c. Sketch particle diagrams for the compounds of A and B that account for these mass ratios. Write
the formula for the compound in each diagram.
Modeling Chemistry
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3. Compounds of copper and chlorine
Atoms of Cu are heavier than Cl atoms
by the ratio in compound A.
A
Compound A: 35.9 g of Cl / 64.1 g of Cu
Compound B: 52.8 g of Cl / 47.2 g Cu
a. Determine the value of the ratio mass Cl in each compound.
A ____
B ____
mass Cu
(assume the smallest ratio is a 1:1 ratio)
Mass of Cu:
B
Mass of Cl:
Mass of Cu:
Mass of Cl:
 compound B compare to that in
b. How does the mass ratio for
compound A?
c. What are the simplest formulas for compounds A and B?
Explain your reasoning.
4. What do you notice about the ratios that help you determine the formulas for these compounds?
Why does that need to be the case?
5. What is the name of the principal that helps us use the mass ratio to determine the formulas for
these compounds?
Modeling Chemistry
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Name
Date
Pd
Chemistry – Unit 4 Worksheet 3b
Use the following information about the masses of elements in each pair of compounds to help you
suggest formulas that account for these ratios.
1. Compounds of nitrogen and oxygen
Compound A: 57.1 g O / 42.9 g C
Compound B: 72.7 g O and 27.3 C
a. Determine the value of the ratio mass of O in each compound.
mass of N
A ____
B _____ (assume the smallest ratio is a 1:1 ratio)
b. How does the mass ratio for compound B compare to that in compound A?
c. What does this ratio mean in terms of particle mass?
d. What are the simplest formulas for compounds A and B? Explain your reasoning and draw a particle
diagram.
A:
B:
2. Compounds of sulfur and oxygen
Compound A: 70.2 g S/ 29.8 g O
a.
Compound B: 44/2 g S/ 55.8 g O
Determine the value of the ratio mass of O in each compound.
mass of S
A ____
B _____ (assume the smallest ratio is a 1:1 ratio)
b. How does the mass ratio for compound B compare to that in compound A?
c. What does this ratio mean in terms of particle mass?
d. What are the simplest formulas for compounds A and B? Explain your reasoning and draw a particle
diagram.
A:
B:
Modeling Chemistry
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