Using Chemical Formulas

7-3

Beaker Breaker

1. Name the following compounds:

CaCl2 = ____________

P3O6 = _____________

FeCl2 =______________

H2SO4 =______________

Formula Masses• sum of the average atomic masses of all the atoms

represented in a formula• (can be of a molecule, formula unit or ion)

• Formula mass of H2O:• 2 (ave. atomic mass of H) +1(ave. at. mass of O)• = 2(1.01 amu) + 1(16.00 amu)• = 2.02 amu + 16.00 amu• = 18.02 amu

Calculate the formula mass of the following:

• sulfuric acid

• calcium nitrate

• phosphate ion

• magnesium chloride

• sulfuric acid

• 98.09 amu H2SO4

• calcium nitrate

• 164.10 amu Ca(NO3)2

• phosphate ion

• 94.97 amu PO43-

• magnesium chloride

• 95.21 amu MgCl2

Molar Masses• sum of the masses of the elements present

in a mole of the molecules or formula units that make up a compound

• Molar mass of water, H2O:• 1 mole H2O = 2 mol H + 1 mol O• 2 mol H x 1.01 g H = 2.02 g H 1 mol H• 1 mol O x 16.00 g = 16.00 g O 1 mol O 18.02 g• Molar mass of water = 18.02 g/mol

What is the molar mass of…

• aluminum sulfide

• sodium nitrate

• barium hydroxide

What is the molar mass of…

• aluminum sulfide

• Al2S3 150.17 g/mol

• sodium nitrate

• NaNO3 85.00 g/mol

• barium hydroxide

• Ba(OH)2 171.35 g/mol

Beaker Breaker

1. Name the following the compounds:

CaBr2 =_______________

H3PO3 =_______________

C3I7 =_________________

CuCl3 = _______________

Gram-Mole Conversions

• What is the mass, in grams, of 0.50000 moles of barium hydroxide?

• Given: 0.500000 mol Ba(OH)2 • Find: g Ba(OH)2

• Know: 1 mol Ba(OH)2 =171.35 g Ba(OH)2

• 0.500000 mol Ba(OH)2 x 171.35 g Ba(OH)2

1 mole Ba(OH)2

• = 85.675 g Ba(OH)2

Using Molar Mass as a conversion factor between “moles” ↔ “mass”

How many moles are in 6.60 g of ammonium sulfate?

• Given: 6.60g (NH4)2SO4

• Find: 0.0499 mol (NH4)2SO4

• Know: 1 mol(NH4)2SO4 = 132.17 g (NH4)2SO4

• (NH4)2SO4 = 2(N) + 8(H) + 1(S) + 4(O)

• = 2(14.01) + 8(1.01) + 1(32.07) + 4(16.00)• 132.17 g/mol

• 6.60g (NH4)2SO4 x 1 mol(NH4)2SO4

132.17 g (NH4)2SO4

• = 0.0499 mol (NH4)2SO4 (4.99 x 10-2mol)

Gram-Mole Conversions

Remember…. 1 mole = 6.02 x 1023 “things”

• How many molecules are in 50.0 g of water?• Given: 50.0 g H2O

• Find: molecules H2O

• Know: 1 mol H2O = 18.02g

• 1 mol H2O = 6.02 x 1023 molecules H2O

• 50.0 g H2O x 1 mol H2O x 6.02 x 1023 molecules

18.02 g H2O 1 mol H2O

• = 1.67 x 1024 molecules H2O

White Board Practice with Partners

How many moles of compound are there in the following

a. 6.60g (NH4)2SO4

b. 4,500g Ca(OH)2

Answers

• A. 0.0500mol

• B. 61mol

White Board Practice with Partners

• How many molecules are there in the following:

a. 25.0g H2SO4

b. 125g of C12H22O11

Answers

• A. 1.53 x1023 molecules

• B. 2.20 x1023 molecules

Beaker Breaker

• Write the formulas of the following compounds

1. Nitric Acid =___________

2. Hydroiodic acid =____________

3. Magnesium Fluoride =____________

4. Tetracarbon nonahydride =__________

Percentage Composition

• % = part x 100

whole

• percentage by mass of each element in a cmpd

Find the % copper in copper(I) sulfide• % Cu = part Cu x 100

whole Cu2S

• % Cu = mass of Cu in 1 mole of Cu2S x 100

mass of 1 mol of Cu2S

Or...% Cu= mass of Cu in 1 mole of Cu2S x 100

molar mass of Cu2S

• Cu2S = 159.17 g/mol (molar mass..on bottom)

• 1 mol Cu2S, there are 2 mol Cu = 127.10 g Cu

(top term)

Find the % copper in copper(I) sulfideKnow:

• % Cu = mass of Cu in 1 mole of Cu2S x 100

mass of 1 mol of Cu2S

• 1 mol of Cu2S = 159.17 g Cu2S

• 1 mol of Cu2S= 2mol Cu = 2(63.546g)= 127.10g

• = 127.10 g Cu x 100

159.17 g Cu2S

• = 79.852% Cu in Cu2S

What is the percent carbon in ammonium carbonate?

Know: (NH4)2CO3

• % C = grams of C in 1 mol (NH4)2CO3 x 100

molar mass of (NH4)2CO3

• 1 mol (NH4)2CO3 = 1 mol C = 12.01 g C

• 1 mol (NH4)2CO3 = 96.11 g (NH4)2CO3

• = 12.01 g C x 100 96.11 g• = 12.50% C

Beaker Breaker

1. Phosphoric acid can be used in orthodontics to roughen the surface of teeth before the placement of braces. Write the chemical formula for phosphoric acid.

2. Explain your method used to arrive to that answer.

Homework CheckPg 236 #25

a. NH41+

Ammonium

b.ClO3-

Chlorate

c. OH-

Hydroxide

d.SO42-

Sulfate

e. NO3-

Nitrate

f.CO32-

Carbonate

g. PO43-

Phosphate

h. CH3COO-

Acetate

i. HCO3-

Bicarbonate

j. CrO42-

Chromate

Mix Review Challenge

Write the name or formula of the following:

1. MgSO3 =______________

2. Sodium Hydroxide = __________

3. Nickel (II) Fluoride =___________

4. P2H3 =__________

Answers

1. Magnesium Sulfite

2. NaOH

3. NiF2

4. Diphosphorus Trihydride

Mix Review Challenge

• Write the name or formula of the following:

5. Sulfurous acid =___________

6. Copper (II) Chloride =_________

7. AlPO4 =____________

8. TetraSulfur Heptoxide =__________

Answers

5. H2SO3

6. CuCl2

7. Aluminum Phosphate

8. S4O7