5/10/2018 1 N'vida E. Houndonougbo Chapter 5:Chemical accounting: Learning Objectives I. Identify balanced and unbalanced chemical equations, and balance equations by inspection. (5.1) II. Write balanced equations for chemical processes. III. Calculate the mass or number of moles of a reactant or product from the mass or number of moles of another reactant or product. (5.4) IV. Define complete and incomplete combustion reactions. V. Discuss the by products of combustion reaction and learn about how carbon monoxide produced by incomplete reaction can affect human health. N'vida E. Houndonougbo Chapter 5: Chemical accounting: Learning Objectives VI. Discuss the reduction of carbon monoxide in the atmosphere using catalytic converters in engines. VII. Define catalysts and how they speed up a chemical reaction by decreasing the energy activation. VIII. Calculate the concentration (Molarity, percent by volume, percent by mass) of a solute in a solution. (5.5) 5/10/2018 2 N'vida E. Houndonougbo Chapter 5: Chemical accounting Suggested Assignment: Chapter 5 • Page 159: Review questions : 4-6 • Page 159: problems: 11-14; 15a,b; 16 • Page 160: Problems: 35-37; 39-46 • Page 363: problems: 5-12 N'vida E. Houndonougbo Chapter 5: Chemical Accounting Outline I. Chemical reactions II. Balancing chemical equations III. Moles and Equation Coefficients IV. Mole–Mole Relationships in chemical reaction V. Stoichiometry Mole and Mass Relationships in Chemical Equations VI. Solution s, solution concentrations, units of concentration 5/10/2018 3 N'vida E. Houndonougbo Chemical changes/Chemical reaction In the course of a chemical change, the reacting substances are converted to new substances. Chemical equations communicate a chemical change using symbols and formulas to represent the elements and compounds involved in a chemical reaction. . N'vida E. Houndonougbo Chemical Change/Chemical reaction  The substances which are present before the change occurs are called the reactants.  The substances which are present after the change occurs are called products. 5/10/2018 4 N'vida E. Houndonougbo Chemical reaction equation 2 H2(g) + O2 (g) → 2 H2O (l) The numbers placed in front of the chemical formulas are called coefficients. The arrow (→) means “yield(s)” or “react(s) to produce. The following are used to denote the state of a species in an equation: (s) = solid (l) =liquid (g)=gas (aq)=aqueous solution . N'vida E. Houndonougbo Chemical reactions • Seven nonmetals occur naturally as diatomic molecules: 1. Hydrogen (H2) 2. Nitrogen (N2) 3. Oxygen (O2) 4. Halogen (F2) 5. Halogen (Cl2) 6. Halogen (Br2) 7. Halogen (I2) • These elements are written as diatomic molecules when they appear in chemical reactions. 5/10/2018 5 N'vida E. .

1. 5/10/2018
1
N'vida E. Houndonougbo
Chapter 5:Chemical accounting:
Learning Objectives
I. Identify balanced and unbalanced chemical equations, and
balance equations by inspection. (5.1)
II. Write balanced equations for chemical processes.
III. Calculate the mass or number of moles of a reactant or
product from the mass or number of moles of another reactant
or product. (5.4)
IV. Define complete and incomplete combustion reactions.
V. Discuss the by products of combustion reaction and learn
about how carbon monoxide produced by incomplete reaction
can affect human health.

2. N'vida E. Houndonougbo
Chapter 5: Chemical accounting:
Learning Objectives
VI. Discuss the reduction of carbon monoxide in the atmosphere
using catalytic converters in engines.
VII. Define catalysts and how they speed up a chemical reaction
by decreasing the energy activation.
VIII. Calculate the concentration (Molarity, percent by volume,
percent by mass) of a solute in a solution. (5.5)
5/10/2018
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N'vida E. Houndonougbo
Chapter 5: Chemical accounting
Suggested Assignment: Chapter 5
• Page 159: Review questions : 4-6

3. • Page 159: problems: 11-14; 15a,b; 16
• Page 160: Problems: 35-37; 39-46
• Page 363: problems: 5-12
N'vida E. Houndonougbo
Chapter 5: Chemical Accounting
Outline
I. Chemical reactions
II. Balancing chemical equations
III. Moles and Equation Coefficients
IV. Mole–Mole Relationships in chemical reaction
V. Stoichiometry
Mole and Mass Relationships in Chemical Equations
VI.
Solution
s, solution concentrations, units of concentration

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N'vida E. Houndonougbo
Chemical changes/Chemical reaction
he course of a chemical change, the reacting
substances are converted to new substances.
change using symbols and formulas to represent the
elements and compounds involved in a chemical
reaction.

5. .
N'vida E. Houndonougbo
Chemical Change/Chemical reaction
occurs are called the reactants.
occurs are called products.
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N'vida E. Houndonougbo
Chemical reaction equation

6. 2 H2(g) + O2 (g) → 2 H2O (l)
called coefficients.
ed to denote the state of a species in an
equation:
(s) = solid (l) =liquid (g)=gas (aq)=aqueous solution
.
N'vida E. Houndonougbo

7. Chemical reactions
• Seven nonmetals occur naturally as diatomic molecules:
1. Hydrogen (H2)
2. Nitrogen (N2)
3. Oxygen (O2)
4. Halogen (F2)
5. Halogen (Cl2)
6. Halogen (Br2)
7. Halogen (I2)
• These elements are written as diatomic molecules when
they appear in chemical reactions.
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N'vida E. Houndonougbo
Chemical reactions
Combustion reaction:
Burning in air is usually referred to as a combustion reaction.
– Hydrocarbons (compounds containing only carbons and
hydrogens) such as gasoline and natural gas are typical fuels
which undergo a combustion reaction.
– In the following combustion reaction, propane (C3H8 ) reacts
with oxygen (O2 ) to produce Carbon dioxide (CO2),
water (H2O) and heat.

9. N'vida E. Houndonougbo
Chemical reactions
Early 1700s Lavoisier:
Law of conservation of mass:
neither created nor destroyed.
the connections between them change.
products must equal the number of atoms

10. of each type in the reactants
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N'vida E. Houndonougbo
Chemical Equations
During a chemical reaction, atoms neither appear or disappear,
only the connections between them change.
This means the number of atoms of each type in the products
must equal the number of atoms of each type in the

11. reactants.
combustion reaction? Discuss in class
N'vida E. Houndonougbo
Balancing Chemical Equations
Practice: Balance the following reaction
Hint: A polyatomic ion such as NO3
- appearing on both sides of an equation
can be treated as a single unit.
Answer: Discuss in class

12. 12
FeBr3(s) + AgNO3(aq) → AgBr(s) + Fe(NO3)3(aq)
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N'vida E. Houndonougbo
Guidelines for Balancing Equations
balance a chemical equation.
ng with the
most complex formula.

13. both sides of the equation.
N'vida E. Houndonougbo
Stoichiometry
Stoichiometry: the quantitative relationship between
reactants and products in a balanced chemical equation.
The coefficients of a balanced chemical equation represent
moles
• Chemists and chemical engineers must perform
calculations based on balanced chemical reactions to
predict the cost of processes.
• The calculations used to avoid using large, excess
amounts of costly chemicals are called stoichiometry

14. calculations.
• Example in class
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N'vida E. Houndonougbo
Mole and Mass Relationships in
Chemical Equations
Steps in a Stoichiometric Calculation:
1. Write and balance the chemical equation for the
reaction.

15. 2. Determine the molar masses of the substances
involved in the calculation.
3. Use the coefficients of the balanced equation to
convert moles of the given substance to moles of
the desired substance.
4. Use the molar mass to convert moles of the
desired substance to grams of the desired
substance.
N'vida E. Houndonougbo
Mole and Mass Relationships in
Chemical Equations
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N'vida E. Houndonougbo
Stoichiometry
Practice in class
N'vida E. Houndonougbo
Complete and Incomplete Combustion
Complete combustion produces CO2 whereas incomplete

17. combustion produces product other than CO2
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N'vida E. Houndonougbo
Complete and Incomplete Combustion
Both reactions proceed simultaneously, competing
for the same reactants, the minor product produced
is called a by-product of the main reaction.

18. N'vida E. Houndonougbo
Complete and Incomplete Combustion
by-product of combustion and produced by incomplete
Combustion.
solid surfaces close to the region of a flame
undergoing incomplete combustion.
diesel-powered engines.
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N'vida E. Houndonougbo
Complete and Incomplete Combustion
Indoor and outdoor Air Pollution
h
concentration.
can be expressed as parts per
million (ppm).
is used when reporting very small
concentrations of substances.

20. Example: Two part per million (2
ppm) of CO in air means that there is
two CO molecule in every one
million molecules of air.
N'vida E. Houndonougbo
Complete and Incomplete Combustion
concentration because it
interferes with O2 transport
from your Lungs to the cells in
your body.

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N'vida E. Houndonougbo
Complete and Incomplete Combustion
Indoor and outdoor Air Pollution:
Carbon monoxide can be produced by:
-Malfunctioning gas or oil furnaces
-Automobile engines
-Fireplaces
-Charcoal grills
-Kerosene heaters

22. N'vida E. Houndonougbo
Complete and Incomplete Combustion
along with extra O2 through a catalytic converter.
verter operates at a high temperature and
converts
CO to CO2.
pt
a reaction without itself being

23. consumed is called a catalyst.
a catalyst is written above the arrow.
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N'vida E. Houndonougbo
Chemical reactions
How does a catalyst speed up the rate of a chemical
reaction?

24. must be broken and energy is required for this to
happen.
place is called Activation energy (Ea).
the activation energy of the reaction.
.
N'vida E. Houndonougbo
Chemical reactions
is to provide a surface on which reactants can meet
therefore increases the number of effective collisions

25. .
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N'vida E. Houndonougbo
Chemistry in water