Name: ___________________________________ Date: __________________ Period: _____
Pre-AP Chem Review Unit 7: Chemical Composition
1.
Write the equation for finding percent composition by mass of an element in a compound:
2.
Define “empirical formula”: _______________________________________________________.
3.
Define “molecular formula”: ______________________________________________________.
4.
Circle any of the following that is an empirical formula? (you may choose more than one)
A. C3H6
B. C4H8O
C. N2O4
D. S4O6
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5.
If 10.01 grams of S combines completely with 19.99 grams of O to form a compound, what is the
percent composition of S in the compound?
6.
What is the percent composition of carbon in Na2CO3?
1
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7.
How many grams of carbon are in 800. grams of CS2 ?
8.
How many grams of hydrogen are in 42.5 grams of H2O ?
9.
What is the empirical formula of a compound that is 74.8% C and 25.2% H?
10.
What is the empirical formula of a compound that is 36.84% N and 63.16% O by mass?
2
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11.
What is the empirical formula of a compound that is 58.75% C, 13.83% H, and 27.42% N by mass?
12.
What is the empirical formula of a compound that is 46.14% C, 7.76% H, and 46.10% O by mass?
13.
3-hexanonol has an empirical formula of C3H7O and a molar mass of about 118 g/mol.
What is the molecular formula of the compound?
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14.
A compound has an empirical formula of CH2 and a molar mass of about 56 g/mol.
What is the molecular formula of the compound?
15.
A certain compound has an empirical formula of C2H4O and a molar mass of about 44 g/mol.
What is the molecular formula of this molecule?
16. Glucose has the following percent composition by mass: 40.0% C, 6.70% H, 53.3% O
The molecular weight of glucose is about 180 g/mol. Using the percent composition and the
molecular weight of glucose, determine its molecular formula.
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