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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