1. Modern Chemistry Chapter 7 Chemical Formulas and Chemical Compounds
Sections 1, 3 & 4
Chemical Names and Formulas
Using Chemical Formulas
Determining Chemical Formulas
Ch 7 Sec 3 Using Chemical Formulas pages

2. Ch 7 Sec 3 Using Chemical Formulas pages 237-244
Monatomic ion
Binary compound
Nomenclature
Oxyanion
Salt
Formula Mass
Percent Composition
Empirical Formula
Chapter Vocabulary
Ch 7 Sec 3 Using Chemical Formulas pages

3. Using Chemical Formulas
Section 3
Using Chemical Formulas
Ch 7 Sec 3 Using Chemical Formulas pages

4. Ch 7 Sec 3 Using Chemical Formulas pages 237-244
Atomic Mass Animation
Ch 7 Sec 3 Using Chemical Formulas pages

5. Ch 7 Sec 3 Using Chemical Formulas pages 237-244
Definitions
Formula Mass –
the mass of any molecule, formula unit or ion.
The sum of all the average atomic masses of all the atoms represented by the formula
Unit: a.m.u.
Molecular mass
Mass of a molecule – in a.m.u.
Ch 7 Sec 3 Using Chemical Formulas pages

6. Ch 7 Sec 3 Using Chemical Formulas pages 237-244
Definitions
Molar mass –
the mass of one mole of atoms of an element
The mass of one mole of molecules or formula units of a compound
Numerically equal to formula mass
Unit: grams/mole (g/mol)
Ch 7 Sec 3 Using Chemical Formulas pages

7. Calculating Formula Mass or Molar Mass
List the elements in the compound.
List the number of atoms of each element.
Multiply each number of atoms by the
Relative atomic mass (for formula mass)
Molar mass (for molar mass)
Add the products.
Ch 7 Sec 3 Using Chemical Formulas pages

8. Calculating Formula Mass or Molar Mass
(NH4)2SO4 N H S O 2 8 1 4
x = 28.02
x =
x = 32.06
x = 64.00 +
Multiply each number of atoms by the
Relative atomic mass (for formula mass)
Molar mass (for molar mass)
Add the products…
List the elements in the compound.
List the number of atoms of each element.
Ch 7 Sec 3 Using Chemical Formulas pages

9. Calculating Formula Mass or Molar Mass
(NH4)2SO4 N H S O 2 8 1 4
x = 28.02
x =
x = 32.06
x = 64.00
The unit is amu for formula mass. The unit is g/mol for molar mass
From the periodic table 4 sig figs
Ch 7 Sec 3 Using Chemical Formulas pages

10. Ch 7 Sec 3 Using Chemical Formulas pages 237-244
1. Find the formula mass of each of the following:
a. H2SO4
b. Ca(NO3)2
c. PO4 3−
d. MgCl2
Practice Page 238
Ch 7 Sec 3 Using Chemical Formulas pages

11. Ch 7 Sec 3 Using Chemical Formulas pages 237-244
2. Find the formula mass of each of the following:
a. Al2S3
b. NaNO3
c. Ba(OH)2
Practice Page 239
Ch 7 Sec 3 Using Chemical Formulas pages

12. Ch 7 Sec 3 Using Chemical Formulas pages 237-244
One mole of …
Nitrogen (balloon)
CdS (yellow)
Water (cylinder)
NaCl (white)
Ch 7 Sec 3 Using Chemical Formulas pages
p. 239

13. Ch 7 Sec 3 Using Chemical Formulas pages 237-244
Mole Animation
Ch 7 Sec 3 Using Chemical Formulas pages

14. Chemical Formulas & Moles2
The formula could stand for 1 molecule of water with 2 hydrogen atoms and 1 oxygen atom… or …
The formula could stand for 1 mole of water molecule which contain 2 moles of hydrogen atoms and 1 mole of oxygen atoms.
Ch 7 Sec 3 Using Chemical Formulas pages

15. Conversions with Compounds 
AMOUNT moles
MOLAR MASS
6.022 x 10 23 x x
MASS grams
PARTICLESmolecules
Ch 7 Sec 3 Using Chemical Formulas pages

16. Conversions with Compounds 
AMOUNT moles
MOLAR MASS
6.022 x 10 23 x x
MASS grams
PARTICLESatoms
Ch 7 Sec 3 Using Chemical Formulas pages

17. Grams-Moles-Molecules Conversions
Ch 7 Sec 3 Using Chemical Formulas pages
p. 240

18. gmol Conversion Animation
Ch 7 Sec 3 Using Chemical Formulas pages
p. 240

19. Dimensional Analysis # & unit given unit given unit wanted x =
Put in numbers to make the numerator equal to the denominator x =
unit given
Fill in units first; then numbers !
Ch 7 Sec 3 Using Chemical Formulas pages

20. Ch 7 Sec 3 Using Chemical Formulas pages 237-244
Dimensional Analysis x x x x =
Arrange the units so that all cancel out except the last one, which should be the one you want.
Ch 7 Sec 3 Using Chemical Formulas pages

21. Ch 7 Sec 3 Using Chemical Formulas pages 237-244
1. How many moles of atoms of each element are there in one mole of the following compounds?
a. Al2S3
b. NaNO3
c. Ba(OH)2
2. Find the molar mass of each of the compounds listed in item 1.
Practice Page 239
Ch 7 Sec 3 Using Chemical Formulas pages

22. Ch 7 Sec 3 Using Chemical Formulas pages 237-244
1. How many moles of compound are there in the following?
a g (NH4)2SO4
b. 4.5 kg Ca(OH)2
2. How many molecules are there in the following?
a g H2SO4
b. 125 g of sugar, C12H22O11
3. What is the mass in grams of 6.25 mol of copper(II) nitrate?
Practice Page 242
Ch 7 Sec 3 Using Chemical Formulas pages

23. % Composition Animation
Ch 7 Sec 3 Using Chemical Formulas pages

24. Percent Composition
(NH4)2SO4 N H S O 2 8 1 4
x = 28.02
x =
x = 32.06
x = 64.00
 = .2120
 =
 = .2426
 = .4843
Find the molar mass of the compound.
Divide the subtotal for each element by the molar mass
Ch 7 Sec 3 Using Chemical Formulas pages

25. Percent Composition
(NH4)2SO4 N H S O
28.02
8.064
32.06
64.00
 = .2120
 =
 = .2426
 = .4843
x100 = 21.20%
x100 = 6.103%
x100 = 24.26%
x100 = 48.43%
Multiply each by 100 to get a percent.
Ch 7 Sec 3 Using Chemical Formulas pages

26. Ch 7 Sec 3 Using Chemical Formulas pages 237-244
Hydrates
Salt which have the ability to bind water molecules within their crystal lattice.
Anhydrous - salts without water
Examples
CuSO4 5H2O
copper(II) sulfate pentahydrate
CoCl2 6H2O
cobalt (II) chloride hexahydrate
Ch 7 Sec 3 Using Chemical Formulas pages

27. Ch 7 Sec 3 Using Chemical Formulas pages 237-244
Hydrates
CuSO4  5H2O
CoCl2  6H2O
Ch 7 Sec 3 Using Chemical Formulas pages

28. Ch 7 Sec 3 Using Chemical Formulas pages 237-244
What percentage of sodium carbonate decahydrate, Na2CO3 10H2O, is sodium carbonate?
1. Find the molar mass of Na2CO3 (the anhydrous compound).
2. Find the mass Na2CO3 10H2O (the hydrate).
3. Divide mass of compound (anhydrous) by mass of the hydrate and multiply by 100.
Ch 7 Sec 3 Using Chemical Formulas pages

29. Percent Composition of a Hydrate
CuSO4  5H2O Cu S O H 1 4 10 5
x = 63.55
x = 32.06
x = 64.00
x = 10.08
x = 80.00
159.61
x 100 =
63.92%
249.69
90.08
x 100 =
36.08%
249.69
249.69
Ch 7 Sec 3 Using Chemical Formulas pages

30. Ch 7 Sec 3 Using Chemical Formulas pages 237-244
What is the percentage of MnCl2 in MnCl2 2H2O?
77.73%
How much water could 100g of anhydrous MnCl2 absorb if the hydrated form is MnCl2 2H2O?
28.64g
Ch 7 Sec 3 Using Chemical Formulas pages

31. Ch 7 Sec 3 Using Chemical Formulas pages 237-244
1. Find the percentage compositions of the following:
a. PbCl b. Ba(NO3)2
2. Find the mass percentage of water in ZnSO4•7H2O.
3. Magnesium hydroxide is 54.87% oxygen by mass. How many grams of oxygen are in 175 g of the compound? How many moles of oxygen is this?
Practice Page 244
Ch 7 Sec 3 Using Chemical Formulas pages

32. Ch 7 Sec 3 Using Chemical Formulas pages 237-244
Section 3 Homework
Ch 7 Sec 3 Using Chemical Formulas pages