Code
C4.1x
C4.1a
C4.1b
C4.1c
Content Expectation
Molecular and Empirical Formulae Compounds have a fixed percent elemental composition. For a compound, the empirical formula can be calculated from the percent composition or the mass of each element. To determine the molecular formula from the empirical formula, the molar mass of the substance must also be known.
Calculate the percent by weight of each element in a compound based on the compound formula.
1. Find the percentage composition of sucrose (C
12
H
22
O
11
).
2. Find the percentage composition of a sample containing 1.29 g of carbon and 1.71 g of oxygen.
3. Find the mass percentage of water in sodium carbonate decahydrate.
4. How many grams of zinc are in a 37.2-gram sample of zinc nitrate?
5. Calculate the mass percent of water in the hydrated form of the solid that has the formula BeC
2
O
4
•3H
2
O.
Calculate the empirical formula of a compound based on the percent by weight of each element in the compound.
6. Find the empirical formula of a compound that contains 75% carbon and 25% hydrogen.
7. Find the empirical formula of a compound that contains 9.03 g magnesium and 3.48 g of nitrogen.
8. A compound is composed of 34.2% sodium, 17.7% carbon, and 47.6% oxygen. Find its empirical formula.
9.
Pure formaldehyde consists of 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen. What is its empirical formula?
10.
Determine the empirical formula of a compound that is
29.0% sodium, 40.5% sulfur, and 30.4 % oxygen by weight.
Use the empirical formula and molecular weight of a compound to determine the molecular formula.
11. Glucose has an empirical formula of CH
2
O. Find its molecular formula if its molecular mass is 180.0 g/mol.
12. A compound has the empirical formula NaCO
2
. If its molecular mass is 134 g/mol, find its molecular formula.
13. A compound with an empirical formula of CH has a molecular weight of 78 g/mol. What is the molecular formula?
14. The simplest formula for vitamin C is C
3
H
4
O
3
. Experimental data indicates that the molecular mass of vitamin C is about

C4.2
C4.2A
C4.2B
C4.2x
C4.2c
C4.2d
180. What is the molecular formula of vitamin C?
15. The simplest formula for butane is C
2
H
5
and its molecular mass is about 60. What is the molecular formula of butane?
Nomenclature All compounds have unique names that are determined systematically.
Name simple binary compounds using their formulae.
16. Name the following compounds. a. MgO b. K
2
S c. AlN d. Ca
3
P
2 e. BeCl
2
Given the name, write the formula of simple binary compounds.
17. Write the formula for the following compounds. a. magnesium sulfide b. gallium chloride c. calcium bromide d. barium iodide e. lithium nitride
Nomenclature All molecular and ionic compounds have unique names that are determined systematically.
Given a formula, name the compound.
18. Name the following compounds. a. AgNO
3 b. Fe
2
O
3 c. CuCl
2 d. SnCO
3 e. BaCrO
4
Given the name, write the formula of ionic and molecular compounds.
19. Write the formula for the following compounds. a.
diphosphorus pentoxide b.
lead(II) nitrate c.
d.
e.
f.
dihydrogen monoxide silicon dioxide sodium chlorate xenon hexafluoride

C4.2e
C4.6x
C4.6a
C4.6b g.
h.
nickel (I) nitrate potassium perchlorate
Given the formula for a simple hydrocarbon, draw and name the isomers.
20.
Name the following hydrocarbons. a.
CH
4 b.
C
3
H
8 c.
C
4
H
10
21.
Name the following branches that may be found in a branched alkane chain. a.
CH
3
CH
2 b.
CH
3 c.
CH
3
CH
3
CH
2
22.
Draw and name all of the structural isomers for C
6
H
14
.
23.
Draw and name all of the structural isomers for C
5
H
12.
Moles The mole is the standard unit for counting atomic and molecular particles in terms of common mass units.
Calculate the number of moles of any compound or element given the mass of the substance.
24. How many grams of AgNO
3
are required to make 25 mL of a
0.80
M solution?
25. How many moles are in 53.8 g of magnesium chloride?
26. Determine the number of moles of CO
2
in 454 grams.
27. Determine the mass in grams of 3.60 mol of H
2
SO
4
.
28. Determine the number of moles in 0.750 grams of Na
2
CO
3
Calculate the number of particles of any compound or element given the mass of the substance.
29. How many grams would 8.1

10 21 molecules of sucrose
(C
12
H
22
O
11
) weigh?
30. How many units are in 0.845 moles of NaNO
3
?
31. How many molecules are in 50.0 g of calcium sulfide?
32. How many atoms are in a 2.0 kg ingot of gold?
33. How many molecules 0.200 gram of H
2
O contains how many molecules? How many atoms of hydrogen are contained in the same sample?