Unit 4B: Balancing Chemical Equations and Classifying

2 H2O + O2 → 2 H2O

Unit 4B: Balancing Chemical

Equations and Classifying Types

of Reactions

Name: _______________________________________ Date: ___________________________ Unit 4- Formulas and Equations Vocabulary Sheet

1

Chemical Formula

Ionic compound

Binary compound

Ternary compound

Diatomic molecule

Polyatomic ion

Coefficient

Subscript

Reactant

Product

Law of Definition proportions

Law of Conservation of Matter

Synthesis

Decomposition

Single Replacement

Double Replacement

Combustion

Name: ____________________________________________ Date: _____________________ Introduction to Balancing Equations and Reactions

2

1. In Chemistry, CO and Co mean different things. How is it shown that they are different AND what does

each one represent?

a. Difference:

b. CO:

c. Co:

Using as Oxygen and as Hydrogen, draw a H2O molecule and a H2O2 molecule in the boxes

below.

H2O H2O2

2. What is a molecule? (Hint: You should have just drawn 2 above)

3. Is H2O2 water? Explain why or why not.

4. What information does a subscript tell you?

5. Draw 2 H2O molecules in the box below:

6. How many hydrogen’s and how many oxygen’s are in the box? Why is it 2 H2O and not just H4O2?

7. What information does a coefficient tell you?

8. Does F2 and 2 F mean the same thing? Explain. (Use pictures if necessary)

a. Similarity-

b. Difference-


3

9. If you are given a molecule of CO2 it means that there is 1 carbon atom bonded to 2 oxygen atoms.

How many carbon’s and oxygen’s do you think are in H(CO)2?

a. Carbon=

b. Oxygen=

When finished: 10. Choose a card, record what is on your card and answer the following questions:

Trial Number 1 2 3 4 5

a.Our card reads:

b. How many molecules are present?

c. How many atoms are in 1 molecule?

d. How many total atoms in all molecules?

11. Choose ONE element in your molecule:

Trial Number 1 2 3 4 5

a. Chosen element:

b. How many atoms of this element are in the molecule?

c. How many total atoms of this element are there?

d. How many total atoms in all molecules?

12. After you have analyzed your first card please choose additional cards and complete as many trials as

you can before time runs out.


4

Total number of molecules present (hint: coefficient)

Number of each type of atom present in one molecule

Total number of atoms present in one molecule

Total number of atoms present in all molecules

a) 2 NH4Cl

b) 3 Al2O3

c) 4 H2SO4

d) 3 KMnO4

e) 4 Na3PO4

f) 2 (NH4)3PO4

g) 5 Ca(OH)2

Name: ___________________________________________________ Date: ________ Period: _______

Balancing Chemical Equations

Why?

Model 1

1) According to Model 1, how many atoms of hydrogen and oxygen are in 1 molecule of water,

H2O?

2) According to Model 1, how many atoms of hydrogen and oxygen are in 1 molecule of H2O2,

hydrogen peroxide?

3) According to Model 1, how many atoms of aluminum, sulfur, and oxygen are in 1 molecule of

aluminum sulfate, Al2(SO4)3?

In a chemical reaction, matter cannot be created or destroyed. The mass of the reactants

in a chemical reaction must be equal to the mass of the products. It is not possible to

start a chemical reaction with 2 atoms of hydrogen and produce 2 atoms of gold.

Similarly, it is not possible to start a chemical reaction with 2 atoms of hydrogen and

produce only 1 atom of hydrogen. When a chemical equation is written, the same

number of each type of atom must appear on both the product and reactant side.

4) How many atoms of hydrogen and oxygen are in 2 molecules of water?

5) How many atoms of hydrogen and oxygen are in 8 molecules of hydrogen peroxide?

6) How many atoms of aluminum, sulfur, and oxygen are in 3 molecules of aluminum sulfate?

7) How would you indicate 2 water molecules using chemical symbols?

8) Using complete sentences, explain the difference between the chemical formulas shown below.

4 H2O and H8O4

Read This!

In a chemical equation, two types of numbers can be used to represent the number of atoms

involved in the reaction. The first type of number is called a subscript. Subscripts are written

after the element symbol in a chemical formula to indicate the number of atoms present in the

compound. The second type of number is called a coefficient. A coefficient is a number

placed in front of a chemical formula to indicate the number of atoms or molecules involved in

a chemical reaction. Chemical equations should always be balanced; that is a chemical

equation should have the same number of atoms on both the reactant and product side of the

equation. When balancing a chemical equation, subscripts are never changed. A coefficient

can be used to ensure an equal number of atoms are found in both the reactant and product

side of a chemical equation.

Model 2

9) In Figure 1, how many molecules of reactants are shown? How many molecules of products are

shown?

10) Explain, using complete sentences, why the reaction represented in Figure 1 is not balanced.

11) In Figure 2, how many molecules of reactants are shown? How many molecules of products

are shown?

12) Using complete sentences, explain why the reaction represented in Figure 2 is not balanced.

13) In Figure 3, how many reactant molecules are shown? How many product molecules are

shown?

14) Using complete sentences, explain why the reaction represented in Figure 3 is balanced.

15) Write a balanced chemical equation to show how hydrogen and oxygen combine to produce

water.

Read This!

Model 3 below illustrates the Haber process, a method used to produce ammonia that was

developed during World War I. When the Allies blocked off all trade routes going to and from

Germany, the Germans lost access to their source of sodium nitrate and potassium nitrate

which were needed to make explosives. In response to the need for a source of nitrates,

chemist Fritz Haber developed what is now known as the Haber Process, which combines

molecular nitrogen from the air with molecular hydrogen to form ammonia gas. (Note: air is

78% nitrogen, so this synthesis is very clever because air is free and abundant.) Using the Haber

Process, the Germans had an uninterrupted source of nitrogen in a form that could be used to

make the nitrates needed for explosives. (http://haberchemistry.tripod.com/)

Model 3

16) Describe what is depicted in Figure 4.

17) Does Figure 4 represent a balanced chemical equation? Why or why not? Explain your

reasoning in terms of the type and number of each atom present.







22) Write a balanced chemical equation for the synthesis of ammonia from hydrogen and nitrogen

gas.

Extension Questions

Using the smallest whole number coefficients, balance the following reactions. Draw diagrams like

those in Model 3 for Equations 1, 2, and 6. You may use the space on the back of this sheet for

your diagrams.

1) _____ HgO → ___ Hg + ___ O2

2) _____ Fe + _____ O2 → _____ Fe2O3

3) _____KClO3 → ____ KCl + ____ O2

4) _____ Ca(OH)2 + _____ H2SO4 → _____ HOH + _____ CaSO4

5) _____ Cu + ______ AgNO3 → ______ Cu(NO3)2 + _____ Ag

6) _____ C2H6 + _____O2 → _____ CO2 + _____ H2O

12

Balancing Chemical Equations

Aim: How can a conservation of mass be shown in a chemical equation? Objective: Balance each chemical equation correctly so the number of atoms of each element is the same on both sides of the reaction.

Do Now: In terms of the atoms present, explain why the reaction below is unbalanced.

+ →

H2 + O2 → H2O Balanced version of the equation:

____ H2 + ____ O2 → ____ H2O

Conservation of Matter

Law of conservation of matter: ____________________________________________________

______________________________________________________________________________

______________________________________________________________________________

• ________________________________________________________________________

• ________________________________________________________________________

________________________________________________________________________

By placing coefficients in front of compounds/elements in a chemical reaction we can balance the reaction.

13

Example 1

____ P + ____ O2 → ____ P4O10

To balance an equation:

1. ____________________________________________________________________________________

____________________________________________________________________________________

2. ____________________________________________________________________________________

3. ____________________________________________________________________________________

4. ____________________________________________________________________________________

5. ____________________________________________________________________________________

_________________________________________________________

a. _________________________________________________________________________________

Example 2:

____ Ca3(PO4)2 + ____ H2SO4 → ____ CaSO4 + ____ H3PO4

14

Example 3: (Demonstrates Rule 5- Tricky combustion equations)

____ C2H6 + ____ O2 → ____ CO2 + ____ H2O

Practice: Balance the following chemical equations and write the lowest whole number coefficients on the lines provided.

1) ____HgO → ____Hg + _____ O2 2) ____Fe + ____O2 → ____Fe2O3

3) ____KClO3 → ____KCl + ____ O2

4) ____ Ca(OH)2 + ____ H2SO4 → ____ HOH + ____ CaSO4 5) ____Cu + ____AgNO3 → ____Cu(NO3)2 + ____ Ag

15

6) ____ C4H8 + ____ O2 → ____ CO2 + _____ H2O

7) ______Al2O3 → ______Al + ______O2 8) ______Fe + ______H2O → ______Fe3O4 + ______H2

9) ______ N2 + ______ H2 → ______ NH3

10) ______ KClO3 → ______ KCl + ______ O2

16

Balancing Equations Practice WS #1

Balance the following chemical equations:

1) ____ N2 + ____ H2 → ____ NH3

2) ____ KClO3 → ____ KCl + ____ O2

3) ____ NaCl + ____ F2 → ____ NaF + ____ Cl2

4) ____ H2 + ____ O2 → ____ H2O

5) ____ Pb(OH)2 + ____ HCl → ____ H2O + ____ PbCl2

6) ____ AlBr3 + ____ K2SO4 → ____ KBr + ____ Al2(SO4)3

7) ____ CH4 + ____ O2 → ____ CO2 + ____ H2O

8) ____ C3H8 + ____ O2 → ____ CO2 + ____ H2O

9) ____ FeCl3 + ____ NaOH → ____ Fe(OH)3 + ____NaCl

10) ____ P + ____O2 → ____P2O5

17

11) ____ Na + ____ H2O → ____ NaOH + ____H2

12) ____ Ag2O → ____ Ag + ____O2

13) ____ S8 + ____O2 → ____ SO3

14) ____ CO2 + ____ H2O → ____ C6H12O6 + ____O2

15) ____ K + ____ MgBr → ____ KBr + ____ Mg

16) ____ HCl + ____ CaCO3 → ____ CaCl2 + ____H2O + ____ CO2

17) ____ HNO3 + ____ NaHCO3 → ____ NaNO3 + ____ H2O + ____ CO2

18) ____ H2O + ____ O2 → ____ H2O2

19) ____ NaBr + ____ CaF2 → ____ NaF + ____ CaBr2

20) ____ H2SO4 + ____ NaNO2 → ____ HNO2 + ____ Na2SO4

18

Balancing Equations Practice WS 1 – Answer Key

Balance the equations below:

1) 1 N2 + 3 H2 → 2 NH3

2) 2 KClO3 → 2 KCl + 3 O2

3) 2 NaCl + 1 F2 → 2 NaF + 1 Cl2

4) 2 H2 + 1 O2 → 2 H2O

5) 1 Pb(OH)2 + 2 HCl → 2 H2O + 1 PbCl2

6) 2 AlBr3 + 3 K2SO4 → 6 KBr + 1 Al2(SO4)3

7) 1 CH4 + 2 O2 → 1 CO2 + 2 H2O

8) 1 C3H8 + 5 O2 → 3 CO2 + 4 H2O

9) 1 FeCl3 + 3 NaOH → 1 Fe(OH)3 + 3 NaCl

10) 4 P + 5 O2 → 2 P2O5

11) 2 Na + 2 H2O → 2 NaOH + 1 H2

12) 2 Ag2O → 4 Ag + 1 O2

13) 1 S8 + 12 O2 → 8 SO3

14) 6 CO2 + 6 H2O → 1 C6H12O6 + 6 O2

15) 1 K + 1 MgBr → 1 KBr + 1 Mg

16) 2 HCl + 1 CaCO3 → 1 CaCl2 + 1 H2O + 1 CO2

17) 1 HNO3 + 1 NaHCO3 → 1 NaNO3 + 1 H2O + 1 CO2

18) 2 H2O + 1 O2 → 2 H2O2

19) 2 NaBr + 1 CaF2 → 2 NaF + 1 CaBr2

20) 1 H2SO4 + 2 NaNO2 → 2 HNO2 + 1 Na2SO4

19

Name ______________________________________________ Date _______

Unit 4B – Class work Practice Sheet #2

Balance the following equations:

1) ________ N2 + ________O2 → ________ N2O5

2) ________ NaCl + ________O2 →________NaClO3

3) ________SnCl4 + ________ (NH4)2S → ________ NH4Cl + ________ SnS2

4) ________Al + ________H2SO4 →________Al2(SO4)3 + ________ H2

5) ________TiCl4 + ________ H2O → ________ TiO2 + ________HCl

6) ________WO3 + ________H2 →________W + ________H2O

7) ________Na3P + ________H(OH) →________NaOH + ________PH3

8) ________Al + ________ O2 →________ Al2O3

9) ________Ag2O → ________Ag + ________O2

10) ______ C8H18 + _______ O2 → ______ CO2 + _______ H2O *****

20

Name ______________________________________________ Date _______

Unit 4B – Balancing Practice #3

Balance the following chemical reactions:

1) ________ NaClO3 → ________NaCl + ________O2

2) ________HCl + ________ Mg(OH)2 → ________MgCl2 + ________ H(OH)

3) ________ Pb + ________ AgNO3 → ________Ag + ________Pb(NO3)2

4) ________ Al + ________ Fe3O4 → ________ Al2O3 + ________Fe

5) ________NaN3 → ________Na + ________N2

6) ________CaO + ________CO2 → ________CaCO3

7) ________Na + ________Cl2 → ________NaCl

8) ________Ca + ________H(OH) → ________Ca(OH)2 + ________H2

9) ________Cl2 + ________ KI → ________KCl + ________I2

10) _______ C4H10 + _______ O2 → ________ CO2 + _______ H2O

Name: ______________________________________________ Date: _________________

21

Types of Chemical Reactions

Describe the features of each of these reactions based on the demonstration.

Synthesis Decomposition

Single Replacement Double Replacement

Other????

Shall We Dance? – Classifying Types of Chemical Reactions

Why? Chemical reactions can be classified into different categories. Four common

types are synthesis, decomposition, single replacement and double replacement. Specific reactions corresponding to these general types are associated with health issues, environmental problems, and manufacturing processes. In order to use chemical reactions or evaluate their effects, you need to be able to identify the type of reaction.

Success Criteria • Identify and differentiate between four types of chemical reactions: synthesis,

decomposition, single replacement and double replacement.

Prerequisites • Reaction equation nomenclature • Balancing equations

New Concepts • Syntheses • Decomposition • Single replacement • Double replacement

© POGIL – 2005 1/6 Authored by Bernadette Halton-Black and Bryan Horan Edited by Linda Padwa and David Hanson, Stony Brook University

Classifying Types of Chemical Reactions

Model 1: Types of Reactions Classification (Type) of Reaction

Example: Using Symbols

Example Reactions

Synthesis A + B AB H2 (g) + 2O2 (g) 2H2O(l)Decomposition XY X + Y 2H2O (l) H2 (g) + 2O2 (g)Single Replacement

A + BC AC + B Al(s) + Cu(NO3)2 (aq) Al(NO3)3(aq) + Cu(s)

Double Replacement

AC + DE AE + DC Pb(NO3)2 (aq) + KI(aq) PbI2(s) + KNO3 (aq)

aq = aqueous, g = gas, s = solid, l = liquid Key Questions 1. As shown in the model, what are the unique characteristics of a synthesis

reaction? 2. As shown in the model, what are the unique characteristics of a decomposition

reaction? 3. As shown in the model, what are the unique characteristics of a single

replacement reaction? 4. As shown in the model, what are the unique characteristics of a double

replacement reaction? Exercise 1. Identify the type of reaction shown in each of the following chemical equations:

KClO3(s) 2KCl(s) + 3O2(g)

AgNO3(aq) + KCl(aq) AgCl(s) + KNO3(aq)

© POGIL – 2005 2/6 Created by Bernadette Halton-Black and Bryan Horan Edited by Linda Padwa and David Hanson, Stony Brook University


Model 2: Analogy - Dancing with Reactants

When you are thinking about the four different types of reactions I'd like you to think about its similarity to dancing (yes, dancing). I'll show you what I mean.

The dance… Amy and Bob were both single. No one was talking about "Amy and Bob"

being together before the dance. They both go to the dance alone. However, they meet at just the perfect time when a song they both adore is playing. They end up holding hands the entire dance. After that fateful meeting no one ever sees Amy without Bob, they are forever referred to as "Amy and Bob". Analysis of the Dancing Model for Chemical Reactions 1. Represent the drama of Amy and Bob described in Model 2 as a chemical

equation? Use A to represent Amy and B to represent Bob.

2. This equation would be classified as a ____________________ reaction.

The dance continues… Later that same evening Xavier and Yasmine, who have been ‘the couple’ forever,

have a heated quarrel and break up. 3. Represent the drama of Xavier and Yasmine as a chemical equation? Use X to

represent Xavier and Y to represent Yasmine. 4. This equation would be classified as a ____________________ reaction.



The dance continues… In their blissful state, Amy and Bob try to help Xavier and Yasmine reconcile their differences. Amy and Bob agree to stop the quarrel by asking Xavier and Yasmine each to dance. 5. Represent Amy and Bob’s attempt to reconcile Xavier and Yasmine as a

chemical equation. 6. This equation would be classified as a ____________________ reaction.

7. What type of reaction is represented in the picture below? Write your own analogy for the reaction illustrated in the picture.

http://www.usoe.k12.ut.us/curr/science/sciber00/8th/matter/sciber/chemtype.htm


http://www.usoe.k12.ut.us/curr/science/sciber00/8th/matter/sciber/chemtype.htm


Exercise 1. Identify the type of reaction in each of the following chemical equations:

a. 2 H2(g) + O2(g) 2 H2O(g)

b. 2 AgNO3(aq) + Cu(s) Cu(NO3)2(aq) + 2 Ag(s)

c. CaCO3(s) CaO(s) + CO2(g)

d. NaI(aq) + Cl2(g) 2NaCl(aq) + I2(s)

Problems 1. For the reaction between aqueous calcium nitrate and aqueous sodium

hydroxide producing the precipitate (solid) calcium hydroxide and aqueous sodium nitrate (a) write a balanced equation for this reaction (b) classify the reaction

2. For the reaction between zinc metal and hydrochloric acid (aqueous) producing zinc chloride (aqueous) and hydrogen gas (a) write a balanced equation for this reaction (b) classify the reaction



3. For the reaction between methane gas and molecular oxygen producing carbon dioxide gas and water vapor (a) write a balanced equation for this reaction (b) Can this reaction be classified as a synthesis, decomposition, single replacement or double replacement reaction? Explain your answer.


Scanned with CamScanner

Scanned with CamScanner

© Evan P. Silberstein, 2002

2H2 + O2 ! 2H2O2(2) + 32 = 2(18)

Chemistry: Form WS5.5.2A Name ______________________________

CHEMICAL REACTIONS Date _________________ Period _____

Balancing EquationsDuring a chemical change, there is no change in mass. Aproperly written chemical equation shows this. The equationbelow is not properly written. It does not show conservation ofmass.

H2 + O2 ! H2O2 + 32 … 18

The reason the equation doesn’t work is simple. There are twoatoms of oxygen in the reactants, but only one in the product. Iftwo molecules of hydrogen react with a molecule of oxygen toform two molecules of water, there are no atoms missing andmass is conserved. The number of molecules is shown with anumber to the left of the formula known as a coefficient. Acoefficient behaves like a multiplier. It’s not necessary to checkthe mass to get a properly written equation. Counting atoms issufficient. When the equation for the formation of water is written properly, 2H2 + O2 ÿ 2H2O, there are 4 hydrogen atomsand two oxygen atoms on both sides of the equation and the mass of the reactants is the same as the mass of the products.Making the number of atoms equal on both sides of the equation is all that is needed. The process is called balancing.

Balance the equations below by writing the correct coefficient in the space before each formula. Coefficient“1” need not be written.

1. ____ H2 + ____ Cl2 ÿ ____ HCl

2. ____ Ca(NO3)2 + ____ H2SO4 ÿ ____ CaSO4 + ____ HNO3

3. ____ Fe + ____ Cl2 ÿ ____ FeCl3

4. ____ Fe + ____ O2 ÿ ____Fe2O3

5. ____ Zn + ____ HCl ÿ ____ ZnCl2 + ____ H2

6. ____ Cu + ____ AgCH3COO ÿ ____Cu(CH3COO)2 + ____ Ag

7. ____ H2SO4 + ____ NaOH ÿ ____Na2SO4 + ____ H2O

8. ____ N2 + ____ H2 ÿ ____ NH3

9. ____ CH4 + ____ O2 ÿ ____ CO2 + ____ H2O

10. ____ S + ____ O2 ÿ ____ SO3

Documents

Unit 4B: Balancing Chemical Equations and Classifying