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## Equation Analogy

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### Every skateboard requires one deck (the board), two trucks (the mounted axles), and four wheels. ... Symbol = shorthand for an atom of an element. ... – PowerPoint PPT presentation

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Title: Equation Analogy

1
Section 7.1
• Equation Analogy
• Imagine that you work at a skateboard shop and
you are in charge of assembling the skateboards.
Every skateboard requires one deck (the board),
two trucks (the mounted axles), and four wheels.
How many trucks do you need?
• 2. The following diagram shows the recipe for
one skateboard. What do you notice about the
relative amounts of each part on either side of
the arrow?

2
Section 7.1
How many trucks do you need?
• 10
• 2. The following diagram shows the recipe for
one skateboard. What do you notice about the
relative amounts of each part on either side of
the arrow?
• There are the same numbers of each part on
either side of the arrow.

3
Terms chapter seven
• Symbol
• Subscript
• Formula
• Equation
• Coefficient
• Atom inventory
• Balanced
• Conservation of atoms

4
Skills chapter 7.1
• How do you do an atom inventory?
• How do you balance an equation?

5
• Symbol shorthand for an atom of an element.
• Formula shorthand for the molecules or basic
units of a compound.
• Equation shorthand for what happens during a
chemical change.

6
• Subscripts in a chemical formula tell how many
atoms of an element are present in that
compounds basic unit
• Coefficients in a balanced equation tell how many
units of each reactant are needed and how many
units of each product are made.
• Coefficients tell the reacting ratio
• 2Na Cl2 ? 2 NaCl

7
• Reactants starting materials
• Products end resulting materials
• Law of conservation of atoms The atoms present
in the reactants are rearranged to form the
products. Atoms are not lost or gained during a
reaction.

8
Burning of Carbon
Figure 2
9
Burning of Carbon
10
Burning of Carbon
11
Burning of Carbon
Atom inventory C 1 C 1 O 2 O
2
12
The formation of water
13
The formation of water
Atom inventory Reactants Products H 4 H
4 O 2 O 2
14
Combustion of Propane
Figue 17
15
Combustion of Propane
Figure 17
16
Combustion of Propane
Figure 17
17
Combustion of Propane
Figure 17
18
• SO2 H2O ?H2SO3
• Reactants Products
• S 1 S1
• O3 O3
• H2 H2 balanced
• 2H2S 3O2 ? 2SO2 2H2O
• reactants products
• H4 H4
• S2 S2
• O6 O6 balanced

19
• 3. CS2 3O2 ? 2SO2 CO2
• reactants products
• C1 C1
• S2 S2
• O6 O6 balanced
• 4. N2 3H2? 2NH3
• reactants products
• N2 N2
• H6 H6 balanced

20
• 5. 2NO O2 ? 2NO2
• reactants products
• N2 N2
• O4 O4 balanced
• 6. 3O2?2O3
• reactants products
• O6 O6 balanced

21
• H2SO3 ? H2O SO2
• reactants products
• H 2 H2
• S1 S1
• O3 O3 balanced
• C6H12O6 6O2 ? 6 CO2 6 H2O
• reactants products
• C6 C6
• H12 H12
• O18 O18 balanced

22
• 9. N2 O2 ? 2NO
• reactants products
• N2 N2
• O2 O2 balanced
• 10. CH4 2O2 ? CO2 2H2O
• reactants products
• C 1 C 1
• H 4 H 4
• O 4 O 4 balanced

23
Answers to Cons. of atoms ex.
• 2a. N2 O2 ? 2NO
• Reactants products
• N2 N2
• O2 O2

24
• 2b. 2NO O2 ? 2NO2
• Reactants products
• N2 N2
• O4 O4

25
• 2c. H2O 2NO2? HNO3 HNO2
• reactants products
• H2 H2
• N 2 N2
• O 5 O5

26
• 2d. N2 3H2 ? 2NH3
• reactants products
• N2 N2
• H 6 H6

27
• 2e. 4NH3 5O2 ? 4 NO 6H2O
• reactants products
• N4 N4
• H12 H12
• O10 O10

28
• 2f. NH3 HNO3 ? NH4NO3
• reactants products
• N2 N 2
• H 4 H 4
• O 3 O 3

29
• 3a. C6H12O6 6O2 ? 6 CO2 6 H2O
• reactants products
• C6 C6
• H12 H12
• O18 O18

30
• 3b. 6 CO2 6 H2O ?C6H12O6 6O2
• reactants products
• C6 C6
• H12 H12
• O18 O18

31
When to balance an equation
• For the equation as it is given do an atom
inventory.
• If the atom inventory is the same on both sides,
the equation is correctly balanced and you are
finished!
• If the atom inventory is not the same, it is not
balanced and you need to balance the equation.

32
CH4 O2 ? H2O CO2
Atom Inventory Reactants Products C 1 C
1 H 4 H 2 O 2 O 3 Equation is not
balanced!
33
How to balance an equation
• A coefficient is changed or added in front of any
formula to increase the number of atoms of a
particular element.
coefficient.

34
CH4 O2 ? 2H2O CO2
Atom Inventory Reactants Products C 1 C
1 H 4 H 4 O 2 O 4 Equation is still
not balanced!
35
• Keep adding and/or changing the coefficients in
front of the formulas until both checklists in
your atom inventory are the same.
• When both lists are the same, the equation is
balanced and you can stop.

36
CH4 2O2 ? 2H2O CO2
Atom Inventory Reactants Products C 1 C
1 H 4 H 4 O 4 O 4 Equation is
balanced!
37
• Only coefficients may be added or changed.
• You may not change any subscripts or formulas in
order to balance the equation.

38
N2 H2 ? NH3 Atom
Inventory Reaactants Products N 2 N 1 H
2 H 3 Equation is not balanced!
39
N2 H2 ? 2NH3 Atom
Inventory Reaactants Products N 2 N 2 H
2 H 6 Equation is not balanced!
40
N2 3H2 ? 2NH3 Atom
Inventory Reaactants Products N 2 N 2 H
6 H 6 Equation is balanced!
41
• CH4 2O2 ? CO2 2H2O
• Zn 2HCl ? H2 ZnCl2
• 2C O2 ? 2CO
• H2 S ? H2S
• 4Al 3O2 ?2Al2O3
• 4Li O2 ? 2Li2O
• 3Mg N2 ? Mg3N2
• 4NH3 5O2 ? 6H2O 4NO

42
http//www.studyworksonline.com
43
Quiz on monday
• Be able to do an atom inventory
• Be able to balance an equation
• Be able to draw or to interpret models for
equations.