Name: _________________________________ Period: _________
Unit 6 Review: The Mole
Fill in the blanks:
1. Formula mass is used for ionic compounds. The formula mass for KBr is
118.99 amu.
2. Molecular mass is used for covalent compounds. The molecular mass of
P2O3 is 109.94 amu.
3. A mole is a unit of measurement that is equal to 6.02 × 1023 representative
particles.
4. Molar mass is the mass in grams of one mole of a substance.
Molar Mass:
5. The molar mass of CaCO3 is 100.08 g/mol.
6. The molar mass of diphosphorus tetraoxide (P2O4) is 125.94 g/mol.
Conversions: (SHOW ALL WORK AND UNITS!)
7. What is the mass of 2.55 moles of Zn?
166.72 g Zn
8. How many moles is 60 grams of barium chloride? BaCl2
0.29 mol BaCl2
9. How many molecule are there in 2.5 moles of water?
1.51 E 24 molecules H2O
10. How many moles are equal to 1.7 X 1022 atoms of calcium?
0.03 mol Ca
11. How many molecules are in 14.2 grams of silver (I) nitrate?
5.03 E 22 molecules AgNO3
12. How many grams are in 6.52E23 formula unit of NaCl?
63.29 g NaCl
Percent composition (Percent by Mass)
13. Find the percent composition of Al2(SO4)3 = 342.14 g/mol
Al = 15.77%
S = 28.11%
O = 56.12%
14. Find the percent composition of Be(OH)2 =43.01 g/mol
Be = 20.95%
O = 74.40%
H = 4.65%
15. Which of the following iron compounds contain the greatest percentage of
iron: pyrite (FeS2), hematite (Fe2O3), siderite (FeCO3)?
Fe2O3
16. Which of the following compounds has a greater percent by mass of
chromium, K2CrO4, or K2Cr2O7?
K2Cr2O7
Empirical and Molecular Formulas:
17. Find the empirical formula of a compound that has 74.51%Pb and 25.49%Cl
PbCl2
2
18. Empirical formula = NH2
Molar mass = 32.06 g/mol. Find the molecular
formula.
N2H4
19. You have a compound with 8 carbon atoms, 8 hydrogen atoms, 2 nitrogen
atoms, and 2 oxygen atoms.
a. Write the molecular formula for this compound
C8H8N2O2
b. Write the empirical formula for this compound
C2H2NO
c. Write the molar mass for this compound
164.08 g/mol
20. A component of protein called serine has an approximate molar mass of 100
g/mole. If the percent composition is as follows, what is the empirical and
molecular formula of serine?
C = 34.95 % H= 6.844 % O = 46.56 % N= 13.59 %
Empirical = C3H7O3N
Molecular = C3H7O3N
3