Non-Copyrighted Material

Making Everything Easier!

StoichiometryFOR

DUMMIES

Learn to:

Balance chemical equations

Calculate molar masses

Find charges of elements and compounds

Write out and solve equations from words

Eric Fortier LsA Learning Center/ La Salle Academy

I really do not know what to write here, but due to my OCD and personal need for detailed replication of things, I need to write something here in fine print. I do not know what they had originally put here, so I figured because it’s in the fine print, no one will read this anyway. ;)

Non-Copyrighted Material

Introduction 2

Finding Charges of Elements 2

Exercises

Compounds 2

Exercises

Significant Digits 2

Scientific Notation 2

Exercises

Balancing Equations 2

Exercises

Stoichiometry 2

Tips and Tricks 2

Appendix 2

Diatomic Pairs

Table of Atomic Masses with Names and Symbols

Periodic Table of Elements

Introduction

Welcome to Stoichiometry for Dummies. In this mini booklet, you will learn about stoi-

chiometry from the bottom, up. Beginning with learning how to find charges, all of the way

through balancing equations and finding ratios of moles.

You may be wondering what a mole is. Many people believe that this type of mole is like

the mole in the ground or on someones face. It is just a common miscommunication, and is fine.

The moles that are being addressed are the universal term for a certain amount of atoms.

6.02x10²³ atoms, Avogadro’s number, is the amount of atoms in a mole.

This short course is made easy by covering the main points of Stoichiometry:

Finding Charges of Elements

Forming Chemical Compounds

Scientific Notation

Significant Digits

Chemical Equations and Balancing Them

Diatomic Pairs

You will be given many tips and tricks that will help you to remember all of the things

you learn her. These tips will help you do to better on tests, understand more in future chemistry,

and act as a reference point.

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Finding Charges of Elements

All compounds and elements have charges which can be found easily.

Exercises

Find the charges of the following ions. The first one is already done for you.

4

All ions in each

column have the

same charge.

All ions in each

column have the

same charge.

Positive Negative

Noble Gases(Non-reactive)

+1

+2 +3 +4 -3 -2 -1

Transition Metals(We’ll deal with these later)

1) K- +12) N-3) Ba-4) Ga-5) As-6) I-7) Cl-8) F-9) Ge-10) Sr-11) Cs-12) Sn-

Compounds

Compounds With Neutral Charges

Compounds are a combination of 2 or more ions. A positive and a negative. The posi-

tive ion is placed before the negative ion. They, when put together, must be balanced.

Compounds With Different Charges

Many For this to happen, in some cases, there must be more than on of a certain ion. For

example, Hydrogen Oxygen. HO. Hydrogen H has a charge of +1. Oxygen O has a charge of -2.

This is not balanced. For this compound to be balanced, there must be an equal positive and neg-

ative charge, which when balanced, will zero each other. To make the compound’s charges zero

each other, a second hydrogen ion must be added. This compound becomes H₂O commonly

known as water. The Subscript in a name means there are that many of the previous ion in the

compound.

Here’s how it works!

Hydrogen by itself has a charge of +1Oxygen by itself has a charge of -2₂1-2 is -1

If you add another hydrogen ion, the charge of hydrogen becomes positive 2

2-2 is 0

Now the compound in balanced.

By using a common multiple between the two charges, you can find out how many ions

are in the compound.

Naming Compounds

5

Uh Oh!Uh Oh!

Combine Ca and As

Ca has a charge of +2

As has a charge of -3Ca +2 As -3

LeastCommonDenominator 6

There must be 3 Ca and 2 As.

The balanced compound is Ca₃As₂

Then divide by the least common multiple

6/2=3 6/3=2

The names of ions change when they are in a compound. The first ion in the compound

stays the same but has a simple variable.

2 of the ion- Di3 of the ion- Tri4 of the ion- Tetra

Hydrogen in water(H₂O) is named Dihydrogen.

The second ion in the compound has a more difficult change. The prefix ide is added in

place of it’s current prefix.

Oxygen becomes Oxide.

Water’s chemical name is Dihydrogen Oxide.

Exercises

Put together the following to form balanced compounds. Then label it with it’s correct name. The first one has already been done for you. Use the Table of Atomic Masses found in the Appendix at the end of the book for naming the compounds.

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1) Li and I- LiILithium Iodide2) Tl and Sb-3) Ge and At-4) Ga and F-5) In and O-6) K and O-7) B and S-8) Mg and P-9) Ra and As-10) H and P-11) C and N-12) Fr and Bi-

Significant Digits

Significant digits are the amount of digits that have a meaning in a numbers ac-

curacy. Significant digits are truly “significant” in near everything in chemistry. It is useful

in every equation, and might just be one of the most important thing to remember in

chemistry.

There are 5 rules that tell which digits are significant within the number:

1) All non zero numbers are significant.

2) Zeros between 2 significant digits are significant.

3) Zeros at the end of a non-decimal number are not significant.

4) Zeros at the beginning of a decimal number are not significant.

5) Zeros at the end of a decimal number are significant.

You are probably thinking that this is not so important, but this is used in formulas, and you need to know how to apply this. There is one more rule to remember.

Round to the least number of significant digits in the given.

The given is what you can see. It is information that is in the problem. The given is what can be used to solve for what is asked. Such as:

7

169,582,734

14,060,502

209,063,700

1.0009094

308.0090700000

9SD

SD is an abbreviation for

Significant Digits

SD is an abbreviation for

Significant Digits

Rule 3 is the only rule that

applies to non-decimal

number.

Rule 3 is the only rule that

applies to non-decimal

number.

8SD

7SD

4SD

5SD

If Molly has $2.06 and she spends $1.08 on a hot dog, how much will the have left?There are 3SD in this given.

That is why you need to know how to find this out. Then you can answer in the correct amount of SD.

Scientific Notation

Converting Numbers into Scientific Notation

In chemistry, there are many numbers are to big to easily handle. Scientific notation, also

called exponential notation, is used to make a number easier to manipulate. Scientific notation is

a way to express any number as a number as big as 1 and less than 10, times some power of 10.

Remember Avogadro’s number? 6.02x10²³. This number is in scientific notation. This is a per-

fect example of how easy scientific notation makes things. Regularly, this number would be:

Being the number of atoms in 1 mole, by itself is fine. In chemistry, though, there are

many moles and this number may be multiplied by large numbers. You can see that multiplying

this by, for example, 87 would be extremely hard to do normally. Multiplying 6.02x10²³ is incon-

testably easier.

Converting a number in scientific notation is not that hard to do. The only thing that is

needed is to move the decimal in the number. Here’s how!

8

602,000,000,000,000,000,000,000

That is not in

scientific notation!

That is not in

scientific notation!

2002985.126 5 4 3 2 1

By moving the decimal to the left 6 spaces, the number is between 1 and 10.

Moving this decimal to the left means that the exponent is a negative. It was moved

six spaces, so this will become x10 ⁶⁻

The number is scientific notation is:2.00298512 x10 ⁶⁻

.00004908191 2 3 4 5

By moving the decimal to the right 5 spaces, the number is between 1 and 10.

Moving this decimal to the left means that the exponent is a negative. It was moved six spaces, so this will become x10⁵

The number is scientific notation is:4.90819 x10 ⁵⁻

When moving the decimal left,the exponent is a negative number.

When moving the decimal right, the exponent is a positive number.

In cases where an answer is already in scientific notation, the answer is as

follows:X x10⁰

For example:6.125

6.125 x10⁰

ExercisesConvert the following numbers into scientific notation. Then round up to the least amount

of significant digits from the given. The first one has been done for you.

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1) What is 48 / 6.01641? 2SD

7.978179678579089 x10⁰

7.9 x10⁰2) What is 14 / 37.26?3) What is 113/14?4) What is 1876.13*147?5) What is 0.09947/1.093?6) What is 149*4.078976?7) What is 145/18?8) What is 100/89?9) What is 15.1614/2?10) What is 0.01450*1409?

Balancing Equations

You now know how to find charges, and make compounds. In this section, you will find out about different types of chemical equations, how to write and balance them. There are 5 types of chemical reactions.

Synthesis (Rust)- Characterized as having one product on one side on the equation.

Single Replacement-has one compound and one element. The reactant replaces an element in the compound. New element and compound are produced.

Double Replacement- two compounds react to form two new compounds.

Combustion- 2 reactants:carbon compound and oxygen. 2 products: CO₂ and H₂0

Decomposition- The breaking down of a compound into it’s elements.

Some times, you will be asked to predict the products with the given reactants. In this case, you will need to know these types to figure out what will happen to the reactants. Some-times, you are given a word problem, and must form the equation and balance it. The only differ-ence is that you must translate the words into elements and compounds. Then carry out the bal-ancing as usual.

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+ions with - ions. Likewise. Never

like charges together.

+ions with - ions. Likewise. Never

like charges together.

Fe + S₈ -> FeS

Leave Hydrogen and

Oxygen to balance last!

Leave Hydrogen and

Oxygen to balance last!

KI + Pb(NO₃)₂ -> KNO₃ + PbI2

CH₄ + O₂ -> CO₂ + H₂O

AgNO₃ -> Ag + N + O₃

Cu + AgNO₃-> AgCu + NO₃

Innies and Outties go together2KI + Pb(NO₃)₂ -> 2KNO₃ + PbI2

Cu + 2AgNO₃-> 2Ag + (NO₃)₂

8 Fe + S₈ -> 8 FeS

CH₄ + 2O₂ -> CO₂ + 2H₂O

2AgNO₃ -> 2Ag + N₂ + 3O₂

Balancing Equations is about getting balance. There has to be the same amount of each compound or element on each side for the chemical equation to be valid. Use numbers in front of the compounds and elements to make each side of the equation have equal amounts of every-thing it contains.

ExercisesBalance the following equations. Then label what kind of reaction the equation is. The

first one has already been done for you.

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3K₂CrO₄ + Al₂S₃ -> 3K₂S + Al₂(CrO₄)₃

Here’s How to balance an

equation.

Here’s How to balance an

equation.

Remember forming compounds. Well this comes into play here. You need to determine how many of each element is in the compound. The compound must be balanced.Luckily, it was already done here.

Next. Label all of the elements and main compounds in the equation. It is easier if the labels are in the same order so checking will be very quick.Number how many of each label are on each side.

K₂CrO₄ + Al₂S₃ -> K₂S + Al₂(CrO₄)₃

K Cr O Al S6 3 12 2 3

K Cr O Al S6 3 12 2 3

As you can see, this is not balanced. Put numbers in front of any of the four compounds until the numbers for the labels are the same. Remember to balance Hydrogen and Oxygen last!Notice how the

number of Oxygen ions fell into place. Now the equation is balanced.

1) HgO -> Hg + O₂

2HgO -> 2Hg + O₂ 2) C₆H₁₃OH + O₂ -> CO₂ + H₂O3) Ca(OH)₂ + H₂SO₄ -> CaSO₄ + HOH

Decomposition

Stoichiometry

You are near your final destination in learning about stoichiometry. In this last section, you will learn why this is so important, and how to carry out the process of STOICHIOMETRY!

This part of chemistry is used a lot in business, mainly in the industry of cosmetics and cologne. It is the way of finding out how much of each reagent is needed for a certain product. It is the relation of moles in a balanced equation. Here’s how it works:

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Grams

Molar Mass= Moles

Ammonium nitrate react with Lithium bicarbonate in a double replacement reaction. if 28g of Lithium bicarbonate is desired, how much Ammonium nitrate is needed in g?

Ammonium Nitrate Lithium Bicarbonate NH₄ NO₃ Li HCO₃

NH₄ +1 | NO₃ -1 + Li +1 | HCO₃-1 -> NH₄HCO₃ + LiNO₃

NH₄NO₃ + LiHCO₃ -> NH₄HCO₃ + LiNO₃

Translate

Form

Rewrite

BalanceNH₄NO₃ + LiHCO₃ -> NH₄HCO₃ + LiNO₃

N H O Li C1 5 6 1 1

N H O Li C1 5 6 1 1

NH₄NO₃ + LiHCO₃ -> NH₄HCO₃ + LiNO₃ Pull out coefficients

1 1 1 1

Use formula to find moles

Find Molar Mass of Lithium Bicarbonate

Molar mass of Lithium is 7.

28/68= 0.41176470588235310.412 moles of Lithium Bicarbonate

LiHCO₃ 687+1+12+(3*16)

X 0.412X=0.412

NH₄NO₃ 8014+4+14+(16*3)

x/80=0.412

x=32.96 grams of NH₄NO₃ Use formula to find grams

Here’s another:

Ammonium Phosphate reacts with radium fluoride. If 445.6 g of NH₄F are desired, how many g of (NH₄)₃PO₄ must react?

NH₄+1PO₄-3 + Ra+2 F-1 -> NH₄+1 F-1 + Ra+2 PO₄-3

2(NH₄)₃PO₄ + 3RaF₂ -> 6NH₄F + Ra₃(PO₄)₂

2(NH₄)₃PO₄ + 3RaF₂ -> 6NH₄F + Ra₃(PO₄)₂

2 3 6 1

X 12.04

13

N H P O Ra F6 24 1 4 3 6

N H P O Ra F6 24 1 4 3 6

NH₄F 3714 4 19

(NH₄)₃PO₄ 149(14*3)+12+31+(16*4)

445.6/37=12.042342342342342312.04 moles of NH₄F

x=4.014 moles

x/149=4.014

x=598.1 g of (NH₄)₃PO₄

Tips and Tricks

Brain Dumping- at the beginning of a test or quiz, write down all of the main materials or

equations that was covered. This is helpful because it acts as a reference point for any time dur-

ing the test. Brain dumping is not considered cheating, so use it to your advantage.

When using scientific notation, use this simple illustration to tell whether the number is to the

positive or negative power. The arrows indicate which way the decimal

was moved. The X indicates the power of 10 the number is multiplied by.

When finding the amounts of Significant digits in a given, tick off SD’s above them. Then write

down the lowest amount of SD’s in the given on the side of the paper near the question number.

When rounding to the correct amount of SD, it may be helpful to draw a line under the number

you are rounding. This line shows how many SD this number will have. Then draw a line be-

tween the new number and the rest os the number, if the number on the right on the line if 5 or

greater, round up the last digit and write the final answer.

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+ <- X -> -

15.2791573458 Round to 4 SD15.2791573458 Greater than 5Final answer:15.80

Appendix

Diatomic Pairs Diatomic pairs are elements that, when alone in an equation, must be doubled.

H₂

O₂

N₂

F₂

Cl₂

Br₂

I₂

15

A useful acronym for remembering these, is:H onestlyO liver,F rancineN everCl eansBr ooms withI odine

Grams

Molar Mass= Moles

Table of Atomic Masses with Names and Symbols

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NameChemical SymbolAtomic NumberNameChemical SymbolAtomic NumberActiniumAc89MeitneriumMt109AluminumAl13MendeleviumMd101AmericiumAm95MercuryHg80AntimonySb51MolybdenumMo42ArgonAr18NeodymiumNd60Arsenic

As33NeonNe10AstatineAt85NeptuniumNp93BariumBa56NickelNi28BerkeliumBk97NiobiumNb41BerylliumBe4NitrogenN7BismuthBi83NobeliumNo102BohriumBh107OsmiumOs76Boro

nB5OxygenO8BromineBr35PalladiumPd46CadmiumCd48PhosphorusP15CalciumCa20PlatinumPt78CaliforniumCf98PlutoniumPu94CarbonC6PoloniumPo84CeriumCe58PotassiumK19Cesi

umCs55PraseodymiumPr59ChlorineCl17PromethiumPm61ChromiumCr24ProtactiniumPa91CobaltCo27RadiumRa88CopperCu29RadonRn86CuriumCm96RheniumRe75DubniumDb105Rho

diumRh45DysprosiumDy66RubidiumRb37EinsteiniumEs99RutheniumRu44ErbiumEr68RutherfordiumRf104EuropiumEu63SamariumSm62FermiumFm100ScandiumSc21FluorineF9Seaborg

iumSg106FranciumFr87SeleniumSe34GadoliniumGd64SiliconSi14GalliumGa31SilverAg47GermaniumGe32SodiumNa11GoldAu79StrontiumSr38HafniumHf72SulfurS16HassiumHs108Tan

talumTa73HeliumHe2TechnetiumTc43HolmiumHo67TelluriumTe52HydrogenH1TerbiumTb65IndiumIn49ThalliumTl81IodineI53ThoriumTh90IridiumIr77ThuliumTm69IronFe26TinSn50Kr

yptonKr36TitaniumTi22LanthanumLa57TungstenW74LawrenciumLr103UraniumU92LeadPb82VanadiumV23LithiumLi3XenonXe54LutetiumLu71YtterbiumYb70MagnesiumMg12Yttrium

Y39ManganeseMn25ZincZn30ZirconiumZr40

Periodic Table of Elements

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