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04:57 PM Unit 1: Stoichiometry Chemistry 2202
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Unit 1: Stoichiometry

Jan 14, 2016

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Unit 1: Stoichiometry. Chemistry 2202. Stoichiometry. Stoichiometry deals with quantities used in OR produced by a chemical reaction. 3 Parts. Mole Calculations (Chp. 2 & 3) Stoichiometry and Chemical Equations (Chp. 4) Solution Stoichiometry (Chp. 6). PART 1 - Mole Calculations. - PowerPoint PPT Presentation
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Page 1: Unit 1:  Stoichiometry

08:09 AM

Unit 1: Stoichiometry

Chemistry 2202

Page 2: Unit 1:  Stoichiometry

08:09 AM

Stoichiometry

Stoichiometry deals with quantities used in OR produced by a chemical reaction

Page 3: Unit 1:  Stoichiometry

08:09 AM

3 Parts

Mole Calculations (Chp. 2 & 3) Stoichiometry and Chemical

Equations (Chp. 4) Solution Stoichiometry (Chp. 6)

Page 4: Unit 1:  Stoichiometry

08:09 AM

PART 1 - Mole Calculations

Isotopes and Atomic Mass (pp. 43 - 46)

Avogadro’s number (pp. 47 – 49) Mole Conversions (pp. 50 - 74)

M, MV, NA, n, m, v, N

Page 5: Unit 1:  Stoichiometry

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Questions

p. 45 #’s 1 – 4p. 46 #’s 1 – 6p. 75 #’s 9 – 12p. 51-53 #’s 5 – 15p. 57 #’s 16 – 19p. 59,60 #’s 20 –

27p. 63,64 #’s 28 - 37

p. 54 #’s 5 – 8p. 65 #’s 2, 4, 5p. 75 #’s 13, 14p. 76 #’s 15, 17–

19,

21-23p. 73 #’s 38 – 43p. 74 #’s 1 – 4p. 76 #’s 26, 27

Page 6: Unit 1:  Stoichiometry

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PART 1 - Mole Calculations

Percent composition: - given mass (p. 79 - 82) - given the chemical formula (p. 83 - 86)

Empirical Formulas (pp. 87 - 94) Molecular Formulas (pp. 95 - 98) Lab: Formula of a Hydrate

Page 7: Unit 1:  Stoichiometry

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Questions

p. 82 #’s 1 – 4p. 85 #’s 5 – 8p. 89 #’s 9 – 12p. 91 #’s 13 – 16p. 97 #’s 17 - 20

p. 103 #’s 23 – 24p. 86 #’s 1, 3 – 6p. 94 #’s 1 - 7p. 106 #’s 1 - 3,

6, 7p. 107 – 109

#’s 5 – 23, 25

Page 8: Unit 1:  Stoichiometry

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Isotopes and Atomic Mass

atomic number - the number of protons in an atom or ion

mass number - the sum of the protons and neutrons in an atom

isotope - atoms which have the same number of protons and electrons but different numbers of neutrons

Page 9: Unit 1:  Stoichiometry

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Isotopes and Atomic Mass eg.

Page 10: Unit 1:  Stoichiometry

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Isotopes and Atomic Mass

1735

1737C l C l

Page 11: Unit 1:  Stoichiometry

08:09 AM

Isotopes and Atomic Mass

1224

1225

1226M g M g M g

not all isotopes are created equal

79 % 10 % 11 %

Page 12: Unit 1:  Stoichiometry

08:09 AM

Isotopes and Atomic Mass

Page 13: Unit 1:  Stoichiometry

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Isotopes and Atomic Mass

atomic mass unit (AMU - p.43)- a unit used to describe the mass of

individual atoms- the symbol for the AMU is u- 1 u is 1/12 of the mass of a carbon-12

atom

Page 14: Unit 1:  Stoichiometry

08:09 AM

Isotopes and Atomic Mass

average atomic mass (AAM)- the AAM is the weighted average of

all the isotopes of an element (p. 45)

p. 14 # 5p. 45 #’s 1 – 4p. 46 #’s 1 – 6 p. 75 #’s 9 - 12

Page 15: Unit 1:  Stoichiometry

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Finding % Abundance

eg. Br has two naturally occurring isotopes. Br-79 has a mass of 78.92 u and Br-81 has a mass of 80.92 u. If the AAM of Br is 79.90 u, determine the percentage abundance of each isotope.

Page 16: Unit 1:  Stoichiometry

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Let x = fraction of Br-79Let y = fraction of Br-81

x + y = 178.92x + 80.92y = 79.90

Finding % Abundance

y = 1 - x

Page 17: Unit 1:  Stoichiometry

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x + y = 178.92x + 80.92y = 79.90

Page 18: Unit 1:  Stoichiometry

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Avogadro’s Number (p. 47)

p. 48

Page 19: Unit 1:  Stoichiometry

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Avogadro’s Number The MOLE is a number used by chemists to

count atoms The MOLE is the number of atoms contained in

exactly 12 g of carbon-12. In honor of Amedeo Avogadro, the number of

particles in 1 mol has been called Avogadro’s number.

Page 20: Unit 1:  Stoichiometry

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How big is Avogadro's number?

An Avogadro's number of soft drink cans would cover the surface of the earth to a depth of over 200 miles.

Avogadro's number of unpopped popcorn kernels spread across the USA, would cover the entire country to a depth of over 9 miles.

Page 21: Unit 1:  Stoichiometry

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If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole.

How big is Avogadro's number?

Page 22: Unit 1:  Stoichiometry

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Avogadro’s Number

1 mole = 6.02214199 x 1023 particles

1 mol = 6.022 x 1023 particles

NA = 6.022 x 1023 particles/mol

Page 23: Unit 1:  Stoichiometry

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Avogadro’s Number

Page 24: Unit 1:  Stoichiometry

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Avogadro’s Number

Number of moles Number of atoms

5 mol

0.01 mol

4.65 x 1024 atoms

8.01 x 1021 atoms

7.72 mol

0.0133 mol

6.022 x 1021 atoms

3.011 x 1024 atoms

Page 25: Unit 1:  Stoichiometry

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Avogadro’s Number

Formulas:

AN

Nn n = # of moles

N = # of particles (atoms, ions, molecules, or formula units)

NA = Avogadro’s #

N = n x NA

Page 26: Unit 1:  Stoichiometry

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How many moles are contained in the following?

a) 2.56 x 1028 Pb atoms

b) 7.19 x 1021 CO2 molecules

Avogadro’s Number

Page 27: Unit 1:  Stoichiometry

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Avogadro’s Number

eg. Calculate the number of moles in 4.98 x 1025 atoms of Al.

eg. How many formula units of Na2SO4 are in 5.69 mol of Na2SO4?

# of Na ions? # of Oxygen atoms?

Page 28: Unit 1:  Stoichiometry

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Avogadro’s Number

1. How many molecules of glucose are in 0.435 mol of C6H12O6?

How many carbon atoms?2. Calculate the number of moles in

a sample of glucose that has 3.56 x 1022 hydrogen atoms.

Page 29: Unit 1:  Stoichiometry

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Avogadro’s Number

pp. 51 – 53: #’s 5 – 15p. 54:  #’s 4 - 8

Page 30: Unit 1:  Stoichiometry

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Molar Mass

The mass of one mole of a substance is called the molar mass of the substance

eg. 1 mole of Pb has a mass of 207.19 g1 mole of Ag has a mass of 107.87 g

Page 31: Unit 1:  Stoichiometry

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Molar Mass

The symbol for molar mass is M and the unit is g/mol

eg. MPb = 207.19 g/mol

MAg = 107.87 g/mol

Page 32: Unit 1:  Stoichiometry

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Molar Mass

The molar mass of a compound is the sum of the molar masses of the elements in the compound

eg. Calculate the molar mass of:a) H2O b) C6H12O6 c) Ca(OH)2

Page 33: Unit 1:  Stoichiometry

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Molar Mass

H2O has 2 hydrogens and 1 oxygen

2 x 1.01 = 2.021 X 16.00 = 16.00

18.02 g/mol

Page 34: Unit 1:  Stoichiometry

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Molar Mass

C6H12O6

6 x 12.01 = 72.0612 x 1.01 = 12.126 x 16.00 = 96.00

180.18 g/mol

Page 35: Unit 1:  Stoichiometry

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Molar Mass

Ca(OH)2

1 x 40.08 = 40.082 x 16.00 = 32.002 x 1.01 = 2.02

74.10 g/mol

Your calculator may not show the zeroes.There should be 2 digits after the decimal when adding molar masses

Page 36: Unit 1:  Stoichiometry

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Molar Mass

p. 57: #’s 16 – 19 & Molar Masses Handout

1. 151.92 g/mol 7. 58.44 g/mol 2. 120.38 g/mol 8. 100.09 g/mol 3. 286.19 g/mol 9. 44.02 g/mol 4. 100.40 g/mol 10. 248.22 g/mol 5. 74.44 g/mol 11. 115.04 g/mol 6. 78.01 g/mol

Page 37: Unit 1:  Stoichiometry

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Molar Mass Calculations

AN

Nn

M

mn

N = n x NA

mass

molar

mass

m = n x M

Avogadro’s #

Page 38: Unit 1:  Stoichiometry

08:09 AM

Molar Mass Calculations

AN

Nn

M

mn

N = n x NA

m = n x M

Page 39: Unit 1:  Stoichiometry

08:09 AM

Molar Mass Calculations

eg. How many moles are in 25.3 g of NO2?

m = 25.3 gMNO2 = 46.01 g/mol

M

mn

mol/g.

g.

0146

325

mol.5500

Page 40: Unit 1:  Stoichiometry

08:09 AM

Molar Mass Calculations

eg. What is the mass of 4.69 mol of water?

n = 4.69 molMwater = 18.02 g/mol

m = n x M = (4.69 mol)(18.02 g/mol) = 84.5 g

Page 41: Unit 1:  Stoichiometry

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Molar Mass Calculations

Practice: p. 59 #’s 20 - 23p. 60 #’s 24 - 27

Page 42: Unit 1:  Stoichiometry

particles(N)

Moles(n)

Mass(m)

5.98 x 1026 Cu atoms

4.50 g H2O

6.15 mol O3

Particle–Mole-Mass Conversions

Page 43: Unit 1:  Stoichiometry

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Molar Mass Calculations

Practice: p. 63 #’s 28 - 33p. 64 #’s 34 – 37p. 76 # 15

moles (n)

mass (m)

particles(N)

x M

÷ M÷ NA

x NA

Page 44: Unit 1:  Stoichiometry

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Molar Mass Calculations

eg. How many molecules are in 26.9 g of water?m = 26.9 gMwater= 18.02 g/mol

NA = 6.022 x 1023 molecules/mol

Find N

Page 45: Unit 1:  Stoichiometry

08:09 AM

Molar Mass Calculations

M

mn

02.18

9.26

= 1.493 mol H2O

N = n x NA

= 1.493 X 6.022 x 1023

= 8.99 x 1023 molecules

Page 46: Unit 1:  Stoichiometry

08:09 AM

Molar Mass Calculations

eg. How many molecules are in 4.78 g of glucose?m = 4.78 gMwater= 180.18 g/mol

NA = 6.022 x 1023 molecules/mol

Find N

Page 47: Unit 1:  Stoichiometry

08:09 AM

Molar Mass Calculations

M

mn

02.18

9.26

= 1.493 mol H2O

N = n x NA

= 1.493 X 6.022 x 1023

= 8.99 x 1023 molecules

Page 48: Unit 1:  Stoichiometry

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Molar Mass Calculations

eg. A sample of Sn contains 4.69 x 1028 atoms. Calculate its mass.

N = 4.69 x 1028 NA = 6.022 x 1023 molecules/mol

MSn = 118.69 g/mol

Find m

Page 49: Unit 1:  Stoichiometry

08:09 AM

Molar Mass Calculations

AN

Nn

23

28

10x022.6

10x69.4

= 77,881 mol

m = n x M

= 77881 mol x 118.69 g/mol

= 9.24 x 10 6 g

Page 50: Unit 1:  Stoichiometry

08:09 AM

Molar Mass Calculations

Practice: p. 63 #’s 28 - 33p. 64 #’s 34 – 37p. 76 # 15

Page 51: Unit 1:  Stoichiometry

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Molar Mass Calculations

Practice:p. 54 #’s 5 - 8p. 65 #’s 2, 4, 5p. 75 #’s 13, 14, p. 76 #’s 15, 17 – 19, 21 -23

Page 52: Unit 1:  Stoichiometry

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Molar Volume

•The volume of a gas increases when temperature increases but decreases when pressure increases .

•The volume of gases is measured under conditions of Standard Temperature and Pressure (STP)

Page 53: Unit 1:  Stoichiometry

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Molar Volume

Standard Pressure – 101.3 kPa Standard Temperature – 0 °C Avogadro hypothesized that equal

volumes of gases at the same temperature and pressure contain equal numbers of molecules.

Page 54: Unit 1:  Stoichiometry

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Molar Volume

Experimental evidence shows the volume of one mole of ANY GAS at STP is 22.4 L/mol

OR MV = 22.4 L/mol

Page 55: Unit 1:  Stoichiometry

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Molar Mass Calculations

AN

Nn

M

mn

N = n x NA

m = n x M

MV

vn

v = n x MV

given volume in Litres

Page 56: Unit 1:  Stoichiometry

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Molar Mass Calculations

moles (n)

mass (m)

particles(N)

x M

÷ M÷ NA

x NA

volume (v)

x MV÷ MV

Page 57: Unit 1:  Stoichiometry

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Molar Volume

p. 73 #’s 38 – 43

p. 74 #’s 1 – 4

p. 76 #’s 26, 27

Page 58: Unit 1:  Stoichiometry
Page 59: Unit 1:  Stoichiometry

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Percent Composition (p. 79)

The mass percent of a compound is the mass of an element in a compound expressed as a percent of the total mass of the compound.

mass percen tm ass o f elem en t

to ta l m ass o f com poundX 100%

Page 60: Unit 1:  Stoichiometry

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Percent Composition

eg. 8.50 g of a compound was analyzed and found to contain 6.00 g of hydrogen and 2.50 g of carbon. Calculate the mass percent for each element.

p. 82 #’s 1 - 4

Page 61: Unit 1:  Stoichiometry

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Percent Composition

mass percent may be found using the formula & the molar mass of a compound.

eg. Find the percentage composition for CH4

Page 62: Unit 1:  Stoichiometry

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Percent Composition

M = 12.01 g/mol + 4(1.01 g/mol) = 12.01 g/mol + 4.04 g/mol

= 16.05 g/mol

% H = (4.04/16.05) X 100% = 25.2 %% C = (12.01/16.05) X 100 % = 74.8 %

p. 85 #’s 5 - 8

Page 63: Unit 1:  Stoichiometry

p. 86 #’s 1, 3 – 6 p. 107 #’s 6 – 10

Page 64: Unit 1:  Stoichiometry

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Empirical Formulas

An empirical formula gives the simplest ratio of elements in a compound.A molecular formula shows the actual number of atoms in a molecule of a compound.Ionic compounds are always written as empirical formulas

Page 65: Unit 1:  Stoichiometry

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Empirical Formulas

Compound Molecular Formula

Empirical Formula

butane C4H10

glucose C6H12O6

water H2O

benzene C6H6

C2H5

CH2O

H2O

CH

Page 66: Unit 1:  Stoichiometry

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Empirical Formulas (p.87)

Page 67: Unit 1:  Stoichiometry

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Empirical Formulas

The empirical formula of a compound may be determined by using the % composition of a given compound.

Page 68: Unit 1:  Stoichiometry

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Empirical Formulas

Method: assume you have 100.0 g of the

compound (ie. change % to g) calculate the moles (n) for each

element divide each n by the smallest n to get

the ratio for the empirical formula

Page 69: Unit 1:  Stoichiometry

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Empirical Formulas

eg. A compound was analyzed and found to contain 87.4% N and 12.6 % H by mass. Determine the empirical formula of the compound.

p. 89 #’s 9 - 12

Page 70: Unit 1:  Stoichiometry

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Empirical Formulas

When finding the EF, the mole ratio may not be a whole number ratio.

eg. A compound contains 84.73% N and 15.27 % H by mass. Determine the empirical formula of the compound.

Page 71: Unit 1:  Stoichiometry

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p. 90

Page 72: Unit 1:  Stoichiometry

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Empirical Formulas

eg. A compound contains 89.91% C and 10.08 % H by mass. Determine the empirical formula of the compound.

p. 91 #’s 13 – 16p. 94 #’s 2-4, 6, 7

Answers on p. 109

Page 73: Unit 1:  Stoichiometry

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MgO Lab

Page 74: Unit 1:  Stoichiometry

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Molecular Formulas The molecular formula of a compound is

a multiple of the empirical formula.

See p. 95

Page 75: Unit 1:  Stoichiometry

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Molecular Formulas

To find the molecular formula we need the empirical formula and the molar mass of the compound

eg. The empirical formula of hydrazine is NH2. The molar mass of hydrazine is 32.06 g/mol. What is the molecular formula for hydrazine?

Page 76: Unit 1:  Stoichiometry

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Molecular Formulas

p. 97 #’s 17 – 20

p. 107, 108 #’s 11 - 14

Page 77: Unit 1:  Stoichiometry

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CHC analyzer (p. 99 – 101)

1. Describe the operation of a carbon hydrogen combustion analyzer.

2. 22.0 g of carbon dioxide and 10.8 g of water is collected in a CHC analysis. Determine the empirical formula of the hydrocarbon.

p. 101 #’s 21, 22

Page 78: Unit 1:  Stoichiometry

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Formula of a hydrate

To determine the formula of a hydrate:

- calculate the moles of water

- calculate the moles of anhydrous compound

- determine the simplest ratio

Page 79: Unit 1:  Stoichiometry

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Formula of a hydrate

eg. Use the data below to determine the value of x in LiCl• xH2O.

mass of crucible = 26.35 g

crucible + hydrate = 42.15 g

crucible + anhydrous compound= 34.94 g

Page 80: Unit 1:  Stoichiometry

mwater = 42.15 – 34.94 = 7.21 g H2O

mLiCl = 34.94 – 26.35 = 8.59 g LiCl

Page 81: Unit 1:  Stoichiometry

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eg. Na2CO3. xH2O

crucible = 15.96 g

crucible + hydrate = 22.19 g

crucible + anhydrous compound = 19.67 g

Page 82: Unit 1:  Stoichiometry

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eg. CoCl2.xH2O

crucible = 151.96 gcrucible + hydrate = 164.35 g crucible + anhydrous compound = 158.23 g

p. 103; # 24 Lab: pp. 104-105

Page 83: Unit 1:  Stoichiometry

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Formula of a hydrate

mass of empty beaker

mass of beaker & hydrate

mass of beaker & anhydrous compound

Page 84: Unit 1:  Stoichiometry

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Review – Chp. 3

p. 86 #’s 1, 3 – 6p. 94 #’s 1 – 7p. 103 # 23p. 106 # 7pp. 107–109 #’s 5 – 23, 25

Page 85: Unit 1:  Stoichiometry

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Test

p. 45 #’s 1 – 4p. 46 #’s 1 – 6p. 75 #’s 9 – 12p. 51-53 #’s 5 – 15p. 57 #’s 16 – 19p. 59,60 #’s 20 –

27p. 63,64 #’s 28 - 37

p. 54 #’s 5 – 8p. 65 #’s 2, 4, 5p. 75 #’s 13, 14p. 76 #’s 15, 17–

19,

21-23p. 73 #’s 38 – 43p. 74 #’s 1 – 4p. 76 #’s 26, 27

Page 86: Unit 1:  Stoichiometry

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Test

p. 82 #’s 1 – 4p. 85 #’s 5 – 8p. 89 #’s 9 – 12p. 91 #’s 13 – 16p. 97 #’s 17 - 20

p. 103 #’s 23 – 24p. 86 #’s 1, 3 – 6p. 94 #’s 1 - 7p. 106 #’s 1 - 3,

6, 7p. 107 – 109

#’s 5 – 23, 25

Page 87: Unit 1:  Stoichiometry

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Stoichiometry (Chp.4)

Stoichiometry is the determination of quantities needed for, or produced by, chemical reactions.

Ratios from balanced chemical equations are used to predict quantities.

Page 88: Unit 1:  Stoichiometry

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Stoichiometry – p. 111

Clubhouse sandwich recipe

Page 89: Unit 1:  Stoichiometry

08:09 AM

Clubhouse sandwich recipe

Slices of Toast

Slices of Turkey

Strips of Bacon

# of Sandwiche

s

12

27

66

100

Fill in the missing quantities:

Page 90: Unit 1:  Stoichiometry

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Mole Ratios

A mole ratio is a mathematical expression that shows the relative amounts of two species involved in a chemical change.

Page 91: Unit 1:  Stoichiometry

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Mole Ratios

A mole ratio Come from a balanced chemical

equation Shows the relative amounts of the

reactants/products in moles Is the coefficient for the required species

in the numerator and the coefficient for the given species in the denominator.

Page 92: Unit 1:  Stoichiometry

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N2(g) + 3 H2 (g) → 2 NH3 (g)

20

66

140

81

Page 93: Unit 1:  Stoichiometry

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C3H8 + 5 O2 → 3 CO2 + 4 H2O

# #required given xcoeffic ien t

coeffic ien trequired

given

How many moles of CO2 are produced when 31.5 mol of O2 react?

Page 94: Unit 1:  Stoichiometry

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C3H8 + 5 O2 → 3 CO2 + 4 H2O

# #required given xcoeffic ien t

coeffic ien trequired

given

How many moles of H2O are produced when 1.35 mol of O2 react?

Page 95: Unit 1:  Stoichiometry

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C3H8 + 5 O2 → 3 CO2 + 4 H2O

# #required given xcoeffic ien t

coeffic ien trequired

given

How many moles of O2 are needed to produce 31.5 mol of CO2?

Page 96: Unit 1:  Stoichiometry

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C3H8 + 5 O2 → 3 CO2 + 4 H2O

# #required given xcoeffic ien t

coeffic ien trequired

given

How many moles of C3H8 are needed to react with 0.369 mol of O2?

Page 97: Unit 1:  Stoichiometry

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C5H12 + O2 → CO2 + H2O

# #required given xcoeffic ien t

coeffic ien trequired

given

How many moles of CO2 are produced when 6.35 mol of O2 react?

Page 98: Unit 1:  Stoichiometry

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Al(s) + Br2(l) → AlBr3(s)

# #required given xcoeffic ien t

coeffic ien trequired

given

How many moles of Br2 are needed to produce 0.315 mol of AlBr3?

p. 115 #’s 4 – 7p. 117 #’s 8 - 10

Page 99: Unit 1:  Stoichiometry

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Mole to Mole Stoichiometry

1. How many moles of nitrogen gas are needed to produce 6.75 mol of NH3 in a reaction with hydrogen gas?

2. How many moles of silver would be produced if 10.0 mol of silver nitrate reacts with copper metal?

3. How many moles of water are produced when 20.6 mol of CH4 burns?

Page 100: Unit 1:  Stoichiometry

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Mole to Mole Stoichiometry

1. How many moles of copper would be produced if 20.5 mol of copper (II) oxide decomposes?

Page 101: Unit 1:  Stoichiometry

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Mole to Mole Stoichiometry

1. How many moles of copper would be produced if 20.5 mol of copper (II) oxide decomposes?

Page 102: Unit 1:  Stoichiometry

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Mass to Mole Stoichiometry

1. How many moles of water are produced when 20.6 g of CH4 burns?

Page 103: Unit 1:  Stoichiometry

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Mass to Mole Stoichiometry

Page 104: Unit 1:  Stoichiometry

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Mole to Mass Stoichiometry

1. What mass of CaCl2 is produced when

4.38 mol of Ca(NO3)2 reacts with NaCl?

Page 105: Unit 1:  Stoichiometry

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Page 106: Unit 1:  Stoichiometry

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Mole to Mass Stoichiometry

1. What mass of CaCl2 is produced when

4.38 mol of Ca(NO3)2 reacts with NaCl?

1. How many moles of copper would be produced if 20.5 g of copper (II) oxide decomposes?

2. How many moles of water are produced when 5.45 gl of C3H8 burns?

Page 107: Unit 1:  Stoichiometry

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Mass to Mass Stoichiometry

eg. Calculate the mass of HCl needed to react with 3.56 g of Fe to produce FeCl2.

Page 108: Unit 1:  Stoichiometry

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Ca(NO3)2 + 2 NaCl → CaCl2 + 2 NaNO3

m ol C aC l2 = 4.38 m ol C a(N O 3)2 x 1 C aC l2

1 C a(N O 3)2

4 .38 m ol C aC l2

Page 109: Unit 1:  Stoichiometry

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2 CuO → 2 Cu + O2

m ol C u = 0.374 m ol C uO x 2 C u

2 C uO 0 .374 m ol C u

Page 110: Unit 1:  Stoichiometry

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C3H8 + 5 O2 → 3 CO2 + 4 H2O

m ol H 2O = 5.45 m ol C 3H 8 x 4 H 2O

1 C 3H 8 21.8 m ol H 2O

Page 111: Unit 1:  Stoichiometry

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Stoichiometry (Chp.4)

Four step stoichiometry:

1. Write a balanced chemical equation

2. Calculate moles given from mass

3. Mole ratio – find moles required

4. Calculate required quantity (mass)

Page 112: Unit 1:  Stoichiometry

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Stoichiometry (Chp.4)

eg. What mass of CO2 gas is produced when 45.9 g of CH4 burns ?

Step #1

CH4 + 2 O2 → CO2 + 2 H2O

45.9 g ? g

Page 113: Unit 1:  Stoichiometry
Page 114: Unit 1:  Stoichiometry
Page 115: Unit 1:  Stoichiometry

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eg. How many moles of HCl needed to react with 3.56 g of Fe to produce FeCl2.

Page 116: Unit 1:  Stoichiometry

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Mole Calculations (p. 121 #13)

3.56 g ? g

= 0.06374 mol Fe

Fe + 2 HCl → FeCl2 + H2

55.85g/mol

g3.56nFe Step #2

Step #3

Fe mol 1

HCl mol 2 x Fe mol 0.06374nHCl

= 0.12748 mol HCl

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Mole Calculations

p. 122 #15Given 32.0 g of sulfur (M = 256.56 g/mol) Find mass of ZnS

#2 n = 0.1247 mol S8

#3 n = 0.9976 mol ZnS(M = 97.45 g/mol)

#4 m = 97.2 g ZnS

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Mole Calculations

p. 123 #18Given 33.5 g of H3PO4 (M = 98.00 g/mol) Find mass of MgO

#2 n = 0.3418 mol H3PO4

#3 n = 0.5128 mol MgO(M = 40.31 g/mol)

#4 m = 20.7 g MgO

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Mole Calculations

p. 123 #17Given 25.0 g of Al4C3 (M = 143.95 g/mol) Find volume of CH4

#2 n = 0.174 mol Al4C3

#3 n = 0.522 mol CH4 (MV = 22.4 L/mol)

#4 m = 11.7 L CH4

Page 120: Unit 1:  Stoichiometry

How many moles of aluminum chloride can be produced from the reaction of chlorine and 10.8 mol of aluminum ?

Cl2(g) + Al(s) → AlCl3(s)

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How many moles of magnesium are needed to react with 27 g of iodine to form magnesium iodide?

Page 122: Unit 1:  Stoichiometry

How many grams of nitrogen are needed to react with 14.0 mol of oxygen to produce nitrogen dioxide ?

N2(g) + O2(g) → NO2(g)

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Mole Calculations (p. 121 #14)

2.34 g ? L

#2 n = 0.05086 mol NO2

#3 n = 0.01272 mol O2

(MV = 22.4 L/mol)

#4 n = (0.01272)(22.4) = 0.285 L O2

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Limiting Reactant (p. 128)

1. 10.0 g of Li requires _______ of Br2

2. 15.0 g of Br2 requires _______ of Li

3. 10.0 g of Li produces _______ of LiBr4. 15.0 g of Br2 produces ______ of LiBr

This problem has _____ g of excess _____and will produce ______ g of LiBr

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Limiting Reactant (p. 128)

10.0 g of Li reacts with 15.0 g of Br2. Calculate the mass of LiBr produced.

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Limiting Reactant (p. 128)

The Limiting Reactant (LR) OR Limiting Reagent (LR) is the substance that is completely used in a chemical reaction.

The Excess Reactant is the reactant that is left over after a reaction is complete.

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Limiting Reactant (p. 128)

eg. 2.00 g of NaI reacts with 2.00 g of Pb(NO3)2. Determine the LR and calculate the amount of PbI2 produced.

write a balanced equation find n for each reactant (Step #2) find moles produced by each

reactant (Step #3)

Page 128: Unit 1:  Stoichiometry

Pb(NO3)2 + 2 NaI → 2 NaNO3 + PbI2

2.00 g 2.00 g

nPb(NO)3 = 2.00 g 331.21 g/mol = 0.006038 mol

nNaI = 2.00 g 149.89 g/mol = 0.013343 mol

Page 129: Unit 1:  Stoichiometry

nPbI2 = 0.006038 mol Pb(NO3)2 x 1 mol PbI2

1 mol Pb(NO3)2

= 0.006038 mol PbI2

nPbI2 = 0.013343 mol NaI x 1 mol PbI2

2 mol NaI

= 0.006672 mol PbI2

mPbI2 = 0.006038 mol x 460.99 g/mol

= 2.78 g PbI2

Page 130: Unit 1:  Stoichiometry

What mass of calcium carbonate will be produced when 20.0 g of calcium phosphate reacts with 15.0 g of sodium carbonate?

(14.2 g)

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What mass of barium hydroxide will be produced when 10.0 g of barium nitrate reacts with 30.0 g of sodium hydroxide? (6.56 g)

Page 132: Unit 1:  Stoichiometry

What volume of hydrogen gas at STP will be produced when 10.0 g of zinc metal reacts with 20.0 g of hydrogen chloride?

Zn + 2 HCl → H2 + ZnCl2

Page 133: Unit 1:  Stoichiometry

Ba(NO3)2 + 2 NaOH → 2 NaNO3 +Ba(OH)2

Page 134: Unit 1:  Stoichiometry
Page 135: Unit 1:  Stoichiometry

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Law of Conservation of Mass (p. 118)

In a chemical reaction, the total mass of reactants always equals the total mass of products.

eg. 2 Na3N → 6 Na + N2

When 500.00 g of Na3N decomposes 323.20 g of N2 is produced. How much Na is produced in this decomposition?

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Law of Conservation of Mass( p. 118)

eg. To produce 90.1 g of water, what mass of hydrogen gas is needed to react with 80.0 g of oxygen?

eg. If 3.55 g of chlorine reacts with exactly2.29 g of sodium, what mass of NaCl willbe produced?

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The theoretical yield is the amount of product that we calculate using stoichiometry

The actual yield is the amount of product obtained from a chemical reaction

Percent yield (p. 137)

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Percent yield (p. 137)

percent y ie ld actua l y ie ld

theoretica l y ie ld x 100

Page 139: Unit 1:  Stoichiometry

DEMO: silver nitrate + copper

Equation:

Mass AgNO3 =

Mass Cu =

Page 140: Unit 1:  Stoichiometry

DEMO: silver nitrate + copper

Mass of filter paper and precipitate =

Mass of empty filter paper =

Mass of precipitate =