Download BalanceEquationsetc

Balancing Chemical Equations
and
Types of Chemical Reactions
Unit 4
What is a chemical equation?
● Chemical equation -
● Parts of an equation:
2Ag + H2S
Ag2S + H2
Reaction symbol
Reactants and Products
● Reactant ● Product -
Subscripts and Coefficients
● Subscript –
●
● Coefficient -
● 2H2 + O2 → 2H2O
Law of Conservation of Mass
● In a chem. rxn, matter is
If an equation obeys the Law of Conservation,
Choosing the order of balancing
Save for later
Start
Pb + PbO2 + H+ → Pb2+ + H2O
Save for later
Start
To balance this equation, use the order: O, H, Pb
Rules of Balancing
1.
Rules of Balancing
A few extra tips:
.
● CH4 + O2 → CO2 + H2O
1 carbon atom
4 hydrogen atoms
2 oxygen atoms
1 carbon atom
2 hydrogen atoms
3 oxygen atoms
●
CH4 + O2 → CO2 + H2O
1 carbon atom
4 hydrogen atoms
4 oxygen atoms
1 carbon atom
4 hydrogen atoms
4 oxygen atoms
DO NOW:
C
1 Carbon atom
O2
1 oxygen molecule
→
→
CO2
1 carbon dioxide molecule
• What are the reactants in this chemical equation?
• What are the products in this chemical equation?
• Are there the same number of atoms on both sides of the
equation?
• Where any atoms destroyed or created?
• Was the Law of Conservation of Matter maintained?
Balancing Equations
Balance the following equation by adjusting coefficients.
N2 + _ H2 → _NH3
reactants products
N
2
1
H
2
3
Balancing Equations
Balance the following equation by adjusting coefficients.
N2 + 3 H2 → 2NH3
reactants products
N
2
21
H
6
2
63
Balancing Equations
Balance the following equation by adjusting coefficients.
_ KClO3 → _ KCl + _ O2
reactants products
K
1
1
Cl
1
1
O
3
2
Balancing Equations
Balance the following equation by adjusting coefficients.
2 KClO3 → 2 KCl + 3 O2
reactants products
K
1
2
12
Cl
1
2
1
2
O
3
6
2
6
DO NOW: Is this equation balanced?
3 H2SO4 + 2 B(OH)3 → B2 (SO4) 3 + 6 H2O
If not, balance it!
Balancing Equations
Balance the following equation:
__C2H6 + __ O2 → __ CO2 + __ H2O
Balancing Equations
Balance the following equation:
__Fe + __ O2 → __ Fe2O3
Balancing Equations
Balance the following equation:
__ HCl + __ Ca(OH)2 → __ CaCl2 + __ H2O
__ H2 + __ O2 → __ H2O
____ P4 + ____ O2 → ____ P2O3
DO NOW
Balance the following equation:
___ Ga + ___ H2SO4
___ Ga2(SO4)3 + ___ H2
5 Types of Chemical Reactions
Combination
A+ B → AB
Decomposition
AB → A + B
Single Displacement
Double Displacement
AB + CD → CB + AD
Combustion
Activity Series
Examples
1.Mg + Cu(NO3)2 →
1.Fe + NA2SO4 →
1.Zn + MnCl2 →
1.2Al + 3SnSO4 →
Examples
1.Mg + Cu(NO3)2 →
Mg(No3)2 + Cu
1.Fe + Na2SO4 → no rxn
1.Zn + MnCl2 → no rxn
1.2Al + 3SnSO4 →
Al2(SO4)3 + 3 SN
DO NOW:
Will a reaction occur in the following single displacement reactions? If yes,
write the products…
1.Fe + Al2O3 →
1.Ca + 2HCl →
The Mole
The Mole … what is it?
• A mole is defined as the number of atoms in exactly 12 grams of
carbon- 12
• The number is called Avogadro’s Number
• One mole of carbon atoms has a mass of 12 grams
Abbreviation for the mole: mol
A Mole of Particles
Contains 6.02 x 1023 particles
• 1 mole C = 6.02 x 1023 C atoms
• 1 mole H2O = 6.02 x 1023 H2O molecules
• 1 mole NaCl = 6.02 x 1023 NaCl molecules
What does a mole count in?
Avogadro’s Number: 6.022142 x 1023 “things” = 1 mole
6.02 × 1023 = 602,000,000,000,000,000,000,000 !
“mole”
6.02 × 1023
1 mole of doughnuts
6.02 × 1023 doughnuts
1 mole of atoms
6.02 × 1023 atoms
1 mole of molecules
6.02 × 1023 molecules
This means a 12 ounce bottle of water would have
19.7 “moles” of water…a much easier-to-work-with number!
Converting to Molar Mass
Molar Mass: The mass for one mole of an atom of molecule
Other terms commonly used for the same meaning:
• Molecular Weight
• Molecular Mass
• Formula Weight
• Formula Mass
Mass of 1 Mole of Atoms
The average atomic mass = grams for 1 mole
Average atomic mass found on periodic table
Element
Mass
1 mole of carbon atoms
12.01 g
1 mole of oxygen atoms
16.00 g
1 mole of hydrogen
atoms
1.01 g
Unit for molar mass: g/mole or g/mol
Calculating a Molecule’s Mass
To find the molar mass of a molecule:
1
Count the number of each type of atom
2
Find the molar mass of each atom on the periodic
table
3
Multiple the # of atoms × molar mass for each atom
4 Find the sum of all the masses
Example Problem - Molar Mass
Example:
Find the
molar
mass for
CaBr2
Example Problem - Molar Mass
1
Example:
Find the
molar
mass for
CaBr2
Count the number of each type of atom
Ca
Br
1
2
Example Problem - Molar Mass
2 Find the molar mass of each atom on the periodic table
Example:
Find the
molar
mass for
CaBr2
Ca
Br
1
2
40.08 g/mole
79.91 g/mole
Example Problem - Molar Mass
3 Multiply the # of atoms x molar mass for each atom
Example:
Find the
molar
mass for
CaBr2
Ca
Br
1
2
x
x
40.08 = 40.08 g/mole
79.91 = 159.82 g/mole
Example Problem - Molar Mass
4 Find the sum of all the masses
Example:
Find the
molar
mass for
CaBr2
Ca
Br
1
2
x
x
40.08 = 40.08 g/mol
79.91 = 159.82 g/mol
199.90 g/mol
1 mole of CaBr2 molecules would
have a mass of 199.90 g
Example of Molar Mass and Parenthesis
Be sure to distribute the subscript outside the parenthesis to each
element inside the parenthesis.
Example:
Find the
molar
mass for
Sr(NO3)2
Example of Molar Mass and Parenthesis
Be sure to distribute the subscript outside the parenthesis to each
element inside the parenthesis.
Example:
Find the
molar
mass for
Sr(NO3)2
Sr
1 × 87.62 g/mole =
87.62 g/mole
N
2 × 14.01 g/mole =
28.02 g/mole
O
6 × 16.00 g/mole =
+ 96.00 g/mole
211.64 g/mole
1 mole of Sr(NO3)2 molecules
would have a mass of 211.64 g
Example of Molar Mass and Parenthesis
Be sure to distribute the subscript outside the parenthesis to each
element inside the parenthesis.
Example:
Find the
molar
mass for
Al(OH)3
Example of Molar Mass and Parenthesis
Be sure to distribute the subscript outside the parenthesis to each
element inside the parenthesis.
Example:
Find the
molar
mass for
Al(OH)3
Al
1 × 26.98 g/mole =
26.98 g/mole
O
2 × 16.00 g/mole =
32.00 g/mole
H
2 × 1.01 g/mole
=
+ 2.02 g/mole
61.00 g/mole
1 mole of Al(OH)3 molecules
would have a mass of 61.00 g
Percent Composition
%
Percent Composition
The percent by mass of each element
compound.
present in a
Example: H2O → 1 mole = 18.01 grams of H2O
2 moles of H: 2 x 1.008 = 2.016 grams
1 mole of O: 1 x 16 = 16 grams
% of H → 2.018 x 100% = 11.19%
88.81%
18.016
% of O → 16 x 100% =
18.016
Example: KMnO4
Find the mass of each element:
K→
Mn →
O (4) →
Example: C6H12O6
First, find the masses of each element:
C (6) →
H (12) →
O (6) →
Using Molar Mass
in Conversions
Example: Moles to grams
How many grams are in 1.25 moles of water?
1
H 2 × 1.01 g/mole =
2.02 g/mole
O 1 × 16.00 g/mole = + 16.00 g/mole
18.02 g/mole
1 mole H2O molecules = 18.02
g
Example: Moles to grams
How many grams are in 1.25 moles of water?
1 mole H2O molecules = 18.02
g
2
1.25 mol
H 2O
18.02 g
HO
1 mol2
H 2O
22.53 g
= _______
H2O
Example: Grams to moles
How many moles are in 25.5 grams of NaCl?
1
Na 1 × 22.99 g/mole = 22.99 g/mole
Cl 1 × 35.45 g/mole = + 35.45 g/mole
58.44 g/mole
1 mole NaCl molecules = 58.44 g
Example: Moles to grams
How many moles are in 25.5 grams of NaCl?
1 mole NaCl = 58.44 g
2
25.5 g NaCl
1
mole NaCl
58.44 g NaCl
0.44
= _______
mole NaCl
Example: Grams to Molecules
How many molecules are in 25.5 grams NaCl?
Think: what steps need to be taken?
1. Convert grams to moles
2. Convert moles to molecules
Example:
Grams toareMolecules
How many molecules
in 25.5 grams NaCl?
1
Na 1 × 22.99 g/mole = 22.99 g/mole
Cl 1 × 35.45 g/mole = + 35.45 g/mole
58.44 g/mole
1 moles NaCl molecules = 58.44 g
1 mol = 6.02×1023
molecules
Example:
Grams toareMolecules
How many molecules
in 25.5 grams NaCl?
2
1 moles NaCl molecules = 58.44 g
1 mol = 6.02×1023
molecules
25.5 g NaCl
1
mol NaCl
58.44 g NaCl
6.02×102 molecules NaCl
3
1
mol NaCl
2.63 ×
= _________
molecules NaCl
1023
Example: Molecules to grams
How many grams is a sample
of 2.75 x 1024 molecules of SrCl2?
Think: what steps need to be taken?
1. Convert molecules to moles
2. Convert moles to grams
Example:
Molecules
to grams
How
many grams
is a sample
of 2.75 x 1024 molecules of SrCl2?
1
Sr 1 × 87.62 g/mole = 87.62 g/mole
Cl 2 × 35.45 g/mole = + 70.90 g/mole
158.52 g/mole
1 moles SrCl2 molecules = 158.52
g
1 mol = 6.02×1023
molecules
Example:
Molecules
to Grams
How
many grams
is a sample
of 2.75 x 1024 molecules of SrCl2?
2
1 moles SrCl2 molecules = 158.52
g
2.75 × 1024
molecules
mol
SrCl2
6.02 ×
molecules
1023
SrCl2
1
SrCl2
158.52 g
SrCl
1
mol 2
SrCl2
7.24
= _________
g
SrCl2