Transcript Chapter 3 Part 2 Review

27 Sept. 2010
Objective: SWBAT write, balance, read
and interpret chemical equations, and
complete mole to mole stoichiometric
calculations.
 Do now: Calculate the mass of just the
oxygen in 5.00 grams of water.
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Agenda
Do now
II. Homework presentation
III. Notes and examples
IV. Practice problems
 Homework: p. 112 #56, 57, 59, 63, 66, 68
(OH)
I.
Decoding Chemical Equations
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2H2(g) + O2(g)  2H2O(l)
Balancing Chemical Equations
Ex 1. KClO3  KCl + O2
Ex 2. C2H6 + O2  CO2 + H2O
Practice Problems
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On your worksheet, practice writing and
balancing chemical equations.
Mole Ratios
Coefficients indicate the number of moles
(or molecules) of each compound
 Ex 1. N2(g) + 3H2(g)  2NH3(g)
1. How many moles of hydrogen gas react
with 1 mole of nitrogen gas?
2. How many moles of ammonia gas are
produced by the reaction of 3 moles of
hydrogen gas in excess nitrogen gas?
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3.
4.
5.
N2(g) + 3H2(g)  2NH3(g)
How many moles of hydrogen gas are
required to react with 15 moles of nitrogen
gas?
How many moles of hydrogen gas are
required to produce 25.0 moles of ammonia
gas?
If 10 moles of nitrogen gas was reacted with
10 moles of hydrogen gas, which would be
completely reacted? Which would be
excess?
Homework
p. 112 #56, 57, 59, 63, 66, 68 (OH)
 Test Thursday (ch. 1, 2, 3)
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28 Sept. 2010
Take out homework
 Objective: SWBAT complete mass to mass
stoichiometric calculations.
 Do now: Gaseous ammonia reacts with
oxygen gas to produce nitrogen monoxide
gas and liquid water. How many moles of
nitrogen monoxide are produced by the
reaction of 0.00300 moles of ammonia in
excess oxygen?
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Agenda
Do now
II. Homework check: on ELMO!
III. Mass to mass stoichiometry examples
and practice problems!
 Homework: p. 113 #70, 72, 74, 76, 78
(MO)
I.
Mass to mass stoichiometric
relationships: Ex 1.
The food we eat is degraded in our bodies to
provide energy for growth and function. A
general equation for this very complex
process is:
C6H12O6 + 6O2  6CO2 + 6H2O
If 856 g of C6H12O6 is consumed by a person
over a certain period, what is the mass of
CO2 produced?
Example 2
All alkali metals react with water to
produce hydrogen gas and the
corresponding alkali metal hydroxide. A
typical reaction is that between lithium
and water:
2Li(s) + 2H2O(l)  2LiOH(aq) + H2(g)
How many grams of Li are needed to
produce 9.89 grams of H2?
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Example 3
Methanol (CH3OH) burns in air according
to the equation
2 CH3OH + 3O2  2CO2 + 4H2O
If 209 g of methanol are used up in the
combustion process, what is the mass of
H2O produced?
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Example 4
The reaction between nitric oxide and
oxygen to form nitrogen dioxide is a key
step in photochemical smog formation:
2NO(g) + O2(g)  2NO2(g)
How many grams of O2 are needed to
produce 2.21 g of NO2?
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Homework

p. 113 #70, 72, 74, 76, 78 (MO)
29 Sept. 2010
Objective: SWBAT determine limiting
reagent, and calculate percent yield.
 Do now: Nitrogen monoxide gas reacts
with oxygen gas to produce nitrogen
dioxide gas. If 5.00 grams of nitrogen
monoxide reacts with excess oxygen, how
many grams of nitrogen dioxide gas are
produced?
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Agenda
Do now
 Homework check (MO)
 Limiting reagent
 Percent Yield
Homework: p. 113 #82, 84, 86, 90, 92, 94
(SR)
Test Monday
Review tomorrow
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Limiting Reagents Ex 1.
Urea is prepared by reacting ammonia with
carbon dioxide:
2NH3(g) + CO2(g) (NH2)2CO(aq) + H2O(l)
In one process, 637.2 g of NH3 are treated with
1142 g of CO2.
a) Which of the two reactants is the limiting
reactant?
b) Calculate the mass of (NH2)2CO formed.
c) How much excess reagent (in grams) is left at
the end of the reaction?
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Example 2
The reaction between aluminium and iron(III)
oxide can generate temperatures approaching
3000oC and is used in welding metals:
2Al + Fe2O3  Al2O3 + 2Fe
In one process, 124 g of Al are reacted with 601 g
of Fe2O3.
a) Calculate the mass (in grams) of Al2O3 formed.
b) How much of the excess reagent is left at the
end of the reaction?
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30 Sept. 2010
Objective: SWBAT determine limiting
reagent, and calculate percent yield.
 Do now:
TiCl4(g) + 2Mg(l)  Ti(s) + 2MgCl2(l)
If 3.54x107 g of TiCl4 are reacted with
1.13x107 g of Mg, calculate the limiting
reagent and the theoretical yield of Ti.

Agenda
Do now
 Homework check (JMS)
 Limiting reagent
 Percent Yield
Homework: p. 113 #90, 92, 94 (SR)
Test Monday
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Reaction Yield
theoretical yield: the amount of product that
would result if all of the limiting reagent
reacted.
actual yield: amount of product actually
obtained from a reaction
actualyield
% yield 
100%
theoreticalyield
Percent Yield Ex 1
Titanium is a strong, lightweight, corrosionresistant metal that is used in rockets, aircraft,
jet engines and bicycle frames. It is prepared by
the reaction of titanium (IV) chloride with
molten magnesium between 950oC and 1150oC:
 TiCl4(g) + 2Mg(l)  Ti(s) + 2MgCl2(l)
3.54x107 g of TiCl4 are reacted with 1.13x107 g of
Mg. a) Calculate the theoretical yield of Ti in
grams. g) Calculate the percent yield if 7.91x106
g of Ti are actually obtained.

Ex 2.
Industrially, vanadium metal, which is
used in steel alloys, can be obtained by
reacting vanadium(V) oxide with calcium
at high temperatures:
5Ca + V2O5  5CaO + 2V
1.54x103 g of V2O5 is reacted with 1.96x103 g
of Ca. a) Calculate the theoretical yield of
V. b) Calculate the percent yield if 803 g
of V are obtained.
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Homework
Test (ch. 1-3) tomorrow
 p. 113 #82, 84, 86, 90, 92, 94 (SR)
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On the test
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Classification and states of matter
Physical and chemical properties
Measurement, handling numbers
Dimensional analysis
Atomic theory and structure
Atomic number, mass number, isotopes
Molecules and Ions
Chemical formulas and names (incl. acids)
Avogadro’s number, moles, molar mass
% composition by mass
Empirical and molecular formulas
Chemical reactions and equations
Mole to Mole and Mass to Mass Stoichiometry
Limiting reagents, reaction yield
Review Game!
With your partner, solve the problem and
show all your work.
 Raise your hand when you are done.
 First group with the correct answer gets
the point and a chance at the bonus point.
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An unfortunate tree is carrying on
photosynthesis in the forest. One morning,
it wakes up with dew on its leaves. The
sunshine immediately begins to evaporate
the dew. Suddenly, a storm rolls in and a
giant wind knocks the tree to the ground. A
limb is struck by lighting and partially
burns. Over the next year, the remaining
parts of the tree rot away. List all the
physical changes in one column and the
chemical changes in another.
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One gallon of gasoline in an automobile’s
engine produces on the average 9.5 kg of
carbon dioxide. Calculate the annual
production of CO2 in kilograms if there are
40 million cars in the US and each car
covers a distance of 5000 mi. at a
consumption rate of 20 miles per gallon.
A transition metal with 26 protons and 24
electrons forms a bond with a polyatomic
ion consisting of phosphorus and four
atoms of oxygen with a charge of 3-.
 a) What type of bond holds this compound
together?
 b) Write the name and formula for this
compound.
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Imagine this compound contains
hydrogen instead of iron.
 a) What type of compound is it?
 b) Write the name and formula for this
compound.
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Imagine that acid lost one oxygen. Name
and write the formula for the newly
formed acid.

Calculate the molar mass of this acid, and
the percent by mass of each element.
A compound is formed by one carbon
atom and four chlorine atoms.
 a) What type of bond holds these atoms
together?
 b) Write the name and formula of this
compound.
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Carbohydrates contain C, H and O, in
which the hydrogen to oxygen ratio is 2:1.
A certain carbohydrate contains 40.0%
carbon by mass. Calculate the empirical
and molecular formulas if the molar mass
is about 178 g.
Lysine, an essential amino acid in the
human body contains C, H, O and N. In
one experiment, the complete combustion
of 2.175 g of lysine gave 3.94 g CO2 and
1.89 g H2O. In a separate experiment,
1.873 g of lysine gave 0.436 g NH3. a)
Calculate the empirical formula.
 b) If the molar mass is about 150 g,
calculate the molecular formula.
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Hydrogen gas can be prepared by reacting
propane gas (C3H8) with steam at about
400oC. The products are carbon
monoxide and hydrogen gas. a) Write a
balanced equation.
 b) How many kilograms of hydrogen gas
can be obtained from 2.84x103 kg of
propane?
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Solid elemental sulfur reacts with a
solution of nitric acid to produce a
solution of sulfuric acid, nitrogen dioxide
gas and water. Write and balance a
chemical equation.
When potassium cyanide reacts with
acids, a deadly poisonous gas, hydrogen
cyanide, is given off.
 KCN(aq) + HCl(aq)  KCl(aq) + HCN(g)
 If a sample of 0.140 g of KCN is treated
with an excess of HCl, calculate the
amount of HCN formed, in grams.
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Nitric oxide (NO) reacts with oxygen gas
to form nitrogen dioxide, a dark brown
gas.
 In one experiment, 0.866 mol of nitric
oxide is mixed with 0.503 mol of oxygen
gas. Calculate which is the limiting
reagent. How many moles of nitrogen
dioxide are produced?
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When heated, lithium reacts with nitrogen
to form lithium nitride.
 What is the theoretical yield of lithium
nitride in grams with 12.3 grams of
lithium are heated with 33.6 grams of
nitrogen?
 If the actual yield of lithium nitride is 5.89
grams, what is the percent yield?
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