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First Name
Period
Date
Block 3 Chemical Reactions
Packet Work List
1. Cover, Vocabulary
2. WCDW
3. Arithmetic of Equations
4. Chemical Calculations
5. Limiting Reagent Percent Yield
6. What is Stoichiometry? Handout
7. Stoichiometry Calculations Handout
8. Reaction Lab done in class
Objective
Balance equations so that the number of reactant elements equals the number of product elements. To find the
percentage of products or reactants in a chemical equation
Standard
Chemistry 3e- Students know how to calculate the masses of reactants and products in a chemical reaction from
the mass of one of the reactants or products and the relevant atomic masses.
Chemistry 3f*- Students know how to calculate percent yield in a chemical reaction.
CCR W8. Gather relevant information from multiple print and digital sources, assess the credibility and
accuracy of each source, and integrate the information while avoiding plagiarism.
Vocabulary
Chemical equation
Mole ratio
Skeleton equation Coefficients
Reactants
Balanced equation Stoichiometry
Products
Focus Questions
This equation shows the formation of iron hydroxide, which is caused by rain meeting iron:
Fe2 + 2H20
2FeOH2
a. Write the six mole ratios that can be derived from this equation.
b. How many moles of Iron are needed to form 2.5 mol of FeOH2?
Vocabulary
1. Chemical equation is the symbolic representation of a chemical reaction wherein the reactant entities
are given on the left-hand side and the product entities on the right-hand side.
2. Skeleton equation is an equation that identifies the reactants and products in a chemical reaction by
their chemical formula but does not quantify them
3. Coefficients is a multiplicative factor in some term of an expression (or of a series); it is usually a
number
4. Balanced equation shows how mass is conserved because it shows how atoms are conserved
5. Stoichiometry is a branch of chemistry that deals with the relative quantities of reactants and products in
chemical reactions
6. Mole ratio is the ratios between the various numerical coefficients of the reactants or products
7. Reactants are a substances that takes part in and undergoes change during a reaction
8. Products are a substances obtained from another substance through chemical change.
WCDW
Warm-up 1
A chemical Reaction is …
Critical Thinking 1
How is a baker similar to a chemist?
Discussion 1
Interpret the given equation in terms of representative particles, number of moles,masses of reactants and
products, and the volumes of each
2K + 2H2O
2KOH + H2
Number of Atoms
Coeff(subscript)
Number of Molecules
Coeff
Number of Mols
Coeff
Mass in Grams
Coeff(mass)
Volume in Liters
Coeff(22.4 L)
2K
2
2H2O
4H 2O
2KOH
2each
H2
2
2
2
2
1
2
2
2
1
2(39)=
2(18)=
2(39+16+1) =
1(2)=
2(22.4)=
2(22.4)=
2(22.4)=
1(22.4)=
Wrap-up 1
I.
The quantitiy of an element can be converted into to _______.
II.
Then the ________ ratio from the balanced equation is used to calculate the
number of moles of the wanted substance.
III.
Finally, the _______ are converted to any unit of measurement related to the
unit mole, as the problem requires.
Warm-up 2
What is missing from the car?
How is this similar to balancing a chemical Equation?
Critical Thinking 2
Describe the process taken to balance an equation.
Discussion 2
Air bags inflate almost instantaneously upon a
car's impact. The effectiveness of air bags is
based on the rapid conversion of a small mass of
NaN3 into a large volume of gas. The gas fills an
air bag, preventing the driver from hitting the
steering wheel or dashboard. The entire reaction
occurs in less than a second. In this section you
will learn how to use a balanced chemical
equation to calculate the amount of product formed in a chemical reaction.
What is the importance for having the air bags start off small?
Wrap-up 2
Explain this statement: “Mass and atoms are conserved in
every chemical reaction, but moles are not necessarily
conserved.”
Warm-up 3
Balance the equation
____ C2 + ___H2 + ___ O2
___C6H12O6
Critical thinking 3
Calculate the molar mass of each reactant and product
Does it follow the Law of Conservation of mass?
Na3PO4 + AgNO3
Na3NO3 + AgPO4
use
Na = 23g
P = 31g
O = 16g
Ag = 108
N = 14
Left Side
1st Na3PO4
3( ) + ( ) + 4( ) =
Right Side
1st Na3NO3
3( ) + ( ) + 3( ) =
2nd
AgNO3
( ) + ( ) + 3( ) =
Total =
Are they the same?
2nd AgPO4
( ) + ( ) + 4( ) =
Total =
Discussion 3
Read the following question, look at the solution, and describe the
process to get the result.
What element in the reaction of 25g of glucose with 40g of Oxygen is
the limiting reactant?
C6H12O6 + 6O2
6CO2 + 6H2O
From chemical Formula
Ratio is 6/1 here we have
1.25/0.1388 = 9.006 to 1
25 g C6H12O6 x 1 mol C6H12O6 = 0.1388 mol C6H12O6
180.06 g C6H12O6
Glucose is the limiting
reactant
40 g O2
x 1mol O2
32 g O2
= 1.25 mol O2
Wrap-up 3
Why is it important to know the limiting
reactant?
1.25 mol O2
0.1388 mol C6H12O6
Arithmetic of Equations
Sample Problem A
Using a Balanced Equation as a Recipe
In a five-day workweek, Tiny Tyke is scheduled to make 640 tricycles. How many wheels should
be in the plant on Monday morning to make these tricycles?
Analyze List the known and the unknown.
Knowns
• number of tricycles = 640 tricycles = 640 FSW3HP2
•F + S + 3W+H + 2P  FSW3HP2
Unknown
• Number of wheels = ? wheels
The desired conversion is tricycles (FSW3HP,)  wheels (W). The balanced equation tells you
that each tricycle has three wheels, or 1 FSW3HP2 = 3 W. The problem can be solved by using the
proper conversion factor derived from this expression.
Calculate Solve for the unknown.
You can write two conversion factors relating wheels
to tricycles.
The desired unit is W, so use the conversion factor
on the left—the one that has W in the numerator.
Multiply the number of tricycles by the conversion
factor.
Evaluate Does the result make sense?
If three wheels are required for each tricycle, and a total of more than 600 tricycles are being
made, then a number of wheels in excess of 1800 is a logical answer. The unit of the known
cancels with the unit in the denominator of the conversion factor, and the answer is in the unit
of the unknown.
Practice Problems
1. Tiny Tike has decided to make 288 tricycles each day. How many tricycle seats, wheels, and
pedals are needed?
2. Write an equation that gives your own "recipe" for making a skateboard.
Sample Problem B
Interpreting a Balanced Equation
Hydrogen Sulfide, which smells like rotten eggs, is found in volcanis gases. The balanced equation for the
burning of Hydrogen Sulfide is:
2H2S + 3O2
2SO2 + 2H2O
Interpret this equation in terms of
a. numbers of representative particles and moles
b. masses of reactants and products
Analyze
a. The coefficients in the balanced equation give the relative number of molecules or moles of reactants and
products
b. A balanced chemical equation obeys the law of conservation of mass.
Calculate
a. 2 molecules H2S + 3 molecules O2
or
2 mol H2S + 3 mol O2
2 molecules SO2 + 2 molecules H2O
2 mol SO2 + 2 mol H2O
b. Multiply the number of moles of each reactant and product by its molar mass:
2 mol H2S + 3 mol O2
2 mol SO2 + 2 mol H2O
2mol(34g/mol) + 3mol(32g/mol)
2 mol(64.1g/mol) + 2mol(18g/mol)
68g + 96g
128g + 36g
164g = 164g
Problems
Does the result make sense?
3. Interpret the equation for the information of water from its elements in terms of numbers of molecules
and moles and volume of gases at STP.
2H2 + O2
2H2O
4. Balance the following equation:
__C2H2 + __O2
___CO2 + ___H2O
Interpret the balanced equation in terms of relative number of moles, volume of gas at STP, and masses of
reactants and products.
Section Assessment
5. How is a balanced equation similar to a recipe?
6. How do chemists use balanced equations?
7. Chemical reactions can be described in terms of what quantities?
8. What quantities are always conserved in chemical reactions?
9. Interpret the given equation in terms of relative numbers of representative particles, numbers of moles, and
masses of reactants and products.
2K + 2H2O  2KOH + H2
10. Balance this equation: ___C2H5OH + __O2
__CO2 + __H2O. Show that the balanced
equation obeys the law of conservation of mass.
Chemical Calculations
Limiting Reagent Percent Yield
What is Stoichiometry?
Stoichiometry Calculations