Reactions amp FormulasIntroductory Chemistry

Canadian AcademyMrT

draft presentation ndash to be updated

+ - ++ -+ +- - +

2

The magnesium is combusting

The magnesium is combining with oxygen

There is a physical change but not a chemical change

Reactions amp FormulasAssessment Statementsbull Name simple ionic and covalent compounds from their formula bull Write formulas for simple ionic and covalent compounds based on

their name bull Write word equations for reactions bull Identify reactants and products in reactions bull Apply state symbols to equations bull Balance simple formula equations bull Identify characteristics of reactions

bull ∆ colourbull ∆ temperature (exothermic or endothermic)bull precipitate formationbull gas productionbull ∆ pH

bull Use conditions for reactions appropriately above the arrow in the equation (heat catalyst etc)

bull Recognise six types of reaction synthesis decomposition single replacement double replacement combustion and neutralisation

Reactions amp FormulasAssessment Statementsbull Name simple ionic and covalent compounds from their formula bull Write formulas for simple ionic and covalent compounds based on

their name bull Write word equations for reactions bull Identify reactants and products in reactions bull Apply state symbols to equations bull Balance simple formula equations bull Identify characteristics of reactions

bull ∆ colourbull ∆ temperature (exothermic or endothermic)bull precipitate formationbull gas productionbull ∆ pH

bull Use conditions for reactions appropriately above the arrow in the equation (heat catalyst etc)

bull Recognise six types of reaction synthesis decomposition single replacement double replacement combustion and neutralisation

Periodic table from httpwwwelementsdatabasecom

non-metals

+1 +2 -1-2-31 2 181716151413

httpcommonswikimediaorgwikiPeriodic_Table_of_Elements

non-metals

+1 +2 -1-2-3

How do we know a reaction has taken placebull ∆ colour (∆ = lsquochange inrsquo)bull ∆ temperature (exothermic or endothermic)bull ∆ pHbull precipitate formationbull gas production

Which of these signs of a chemical reaction have we come across in our reactions so far

Naming IonsRemember metals bonding with non-metals form ionic bonds

Some ions are polyatomic This means they are made of groups of atoms which stay together in reactions ndash such as carbonates

What do the elemental anions have in common in their name

What do the polyatomic anions have in common in their name (except hydroxide)

What is the difference between the iron (II) and iron (III) ions

Naming Ionic CompoundsRules bull balance the chargesbull keep polyatomic ions together

Examples

HCl hydrogen chloride

NaOH sodium hydroxide

ZnCl2 zinc chloride

Fe2O3 iron oxide

NaOH sodium hydroxide

Pb(NO3)2 lead nitrate

Naming Covalent MoleculesRemember You can only correctly call it a molecule if it is covalently-bonded

Covalent bonds form between non-metal atoms

Name the compound this waybull You donrsquot need mono- if the first atom is singlebull Use the prefixes for all other atoms

Examples

CO carbon monoxideCO2 carbon dioxideN2O3 dinitrogen trioxide

CF4 N2O4 N2H4 H2O

Conventions in Writing Reactions

Mg O2+ MgOheat

magnesium + oxygen magnesium oxide(s) (g) (s)

conditions for reaction to occur (eg heat catalysts)

ldquogivesrdquo

symbol equation

word equation

State symbols need to be included(s) solid ndash this included precipitates(g) gas(l) liquid(aq) aqueous solution solutes dissolved in water

state symbols should be subscripted

reactants products

Wait

Mg O2+ MgOheat

magnesium + oxygen magnesium oxide(s) (g) (s)

The reactants and products are not balanced

Balancing Equations

Simple steps for balancing equations1 List amp count the elements and groups on

each side of the equation Donrsquot split polyatomic ions

2 Select the compound with the greatest number of atoms (not counting H and O)

3 Balance the atoms in this compound on both sides of the equation

4 Donrsquot change any compounds5 Balance any groups such as polyatomic

ions 6 Finish up with H and O

Mg O2+ MgOheat

magnesium + oxygen magnesium oxide(s) (g) (s)

Reactants Products

Mg 1 1

O 2 1

The Law of Conservation of Mass states that matter is neither created nor destroyed There MUST be the same number of atoms on each side of the equation

Balancing Equations

Simple steps for balancing equations1 List amp count the elements and groups on

each side of the equation Donrsquot split polyatomic ions

2 Select the compound with the greatest number of atoms (not counting H and O)

3 Balance the atoms in this compound on both sides of the equation

4 Donrsquot change any compounds5 Balance any groups such as polyatomic

ions 6 Finish up with H and O

Mg O2+ MgOheat

magnesium + oxygen magnesium oxide(s) (g) (s)

Reactants Products

Mg 1 1 2

O 2 1 2

The Law of Conservation of Mass states that matter is neither created nor destroyed There MUST be the same number of atoms on each side of the equation

2

Balancing Equations

Simple steps for balancing equations1 List amp count the elements and groups on

each side of the equation Donrsquot split polyatomic ions

2 Select the compound with the greatest number of atoms (not counting H and O)

3 Balance the atoms in this compound on both sides of the equation

4 Donrsquot change any compounds5 Balance any groups such as polyatomic

ions 6 Finish up with H and O

Mg O2+ MgOheat

magnesium + oxygen magnesium oxide(s) (g) (s)

Reactants Products

Mg 1 2 1 2

O 2 1 2

The Law of Conservation of Mass states that matter is neither created nor destroyed There MUST be the same number of atoms on each side of the equation

2 2

Two molecules of Mg are needed to react with one molecule of O2 giving 2 MgO

Types of Reactions

synthesisdecomposition

neutralization combustion

singlereplacem

entdo

uble

repl

acem

ent

A + B AB AB A + B

AB + C CB + A AB + CD AD + BC

H[A] + [B]OH [B][A] + H2O CxHx + O2 CO2 + H2Oheat

Synthesis Reactions

+

These can be simplified as A + B ABWhere two or more reactants combine to make a single product

carbon dioxide + water carbonic acid(g) (l) (aq)

Reactants Products

C

O

H

CO2 H2O+ H2CO3

balanced

Synthesis Reactions

+

These can be simplified as A + B ABWhere two or more reactants combine to make a single product

carbon dioxide + water carbonic acid(g) (l) (aq)

Reactants Products

C 1 1

O 3 3

H 2 2

CO2 H2O+ H2CO3

balanced

Types of Reactions

synthesisdecomposition

neutralization combustion

singlereplacem

entdo

uble

repl

acem

ent

A + B AB AB A + B

AB + C CB + A AB + CD AD + BC

H[A] + [B]OH [B][A] + H2O CxHx + O2 CO2 + H2Oheat

Decomposition ReactionsThese can be simplified as AB A + BWhere a single reactant breaks down into component elements or compounds

+

hydrogen peroxide water + oxygen(l)(l)

O2H2O +H2O2(g)

MnO2

MnO2 acts as a catalyst in this reaction It allows the reaction to take place more quickly but is not used upWe put it above the arrow It can be recovered and reused in another reaction

MnO2

MnO2

Decomposition ReactionsThese can be simplified as AB A + BWhere a single reactant breaks down into component elements or compounds

+

hydrogen peroxide water + oxygen(l)(l)

O2H2O +H2O2(g)

MnO2

MnO2 acts as a catalyst in this reaction It allows the reaction to take place more quickly but is not used upWe put it above the arrow It can be recovered and reused in another reaction

MnO2

Decomposition ReactionsThese can be simplified as AB A + BWhere a single reactant breaks down into component elements or compounds

+

hydrogen peroxide water + oxygen(l)(l)

O2H2O +H2O2(g)

MnO2

MnO2 acts as a catalyst in this reaction It allows the reaction to take place more quickly but is not used upWe put it above the arrow It can be recovered and reused in another reaction

Enzymes are catalysts found in living organisms They are proteins with an active site

Decomposition ReactionsThese can be simplified as AB A + BWhere a single reactant breaks down into component elements or compounds

+

hydrogen peroxide water + oxygen(l)(l)

Reactants Products

O

H

O2H2O +H2O2

balanced

(g)

MnO2

Decomposition ReactionsThese can be simplified as AB A + BWhere a single reactant breaks down into component elements or compounds

+

hydrogen peroxide water + oxygen(l)(l)

Reactants Products

O 2 3

H 2 2

O2H2O +H2O2

balanced

(g)

MnO2

Decomposition ReactionsThese can be simplified as AB A + BWhere a single reactant breaks down into component elements or compounds

+

hydrogen peroxide water + oxygen(l)(l)

Reactants Products

O 2 3 4

H 2 2 4

O2H2O +H2O2

balanced

(g)

MnO2 2

Decomposition ReactionsThese can be simplified as AB A + BWhere a single reactant breaks down into component elements or compounds

+

hydrogen peroxide water + oxygen(l)(l)

Reactants Products

O 2 4 3 4

H 2 4 2 4

O2H2O +H2O2

balanced

(g)

MnO22 2

Decomposition ReactionsThese can be simplified as AB A + BWhere a single reactant breaks down into component elements or compounds

copper (II) sulphate pentahydrate copper (II) sulphate + water

(g)(s)

H2O+CuSO45H2OHeat 5CuSO4

(s)

Heat

Decomposition ReactionsThese can be simplified as AB A + BWhere a single reactant breaks down into component elements or compounds

copper (II) sulphate pentahydrate copper (II) sulphate + water

(g)(s)

H2O+CuSO45H2OHeat 5CuSO4

(s)

+Heat

28

Danger dihydrogen monoxideLethal if inhaled

Found in disaster zones

Reduces the effectiveness of brakes

Found in tumour cells viruses and deadly bacteria

Contributes to electrocutions

httpwwwdhmoorgfactshtmlFind out more about this lethal substance

Used by terrorists and pirates

Danger dihydrogen monoxideLethal if inhaled

Found in disaster zones

Reduces the effectiveness of brakes

Found in tumour cells viruses and deadly bacteria

Contributes to electrocutions

httpwwwdhmoorgfactshtmlFind out more about this lethal substance

Used by terrorists and pirates

30

Ionic Covalent

bull Donrsquot use mono- di- etc in prefixes bull Cation then anion eg lithium bromide bull Donrsquot break up polyatomic ions

Remember that in ionic compounds the sum of the charges must be zero Therefore sodium sulphide is Na2S not NaS

bull Endings usually ndashide bull Donrsquot need mono- prefix for first

atom if it is single (eg CH4)bull Name in order of the periodic

table but H is before O

Types of Reactions

synthesisdecomposition

neutralization combustion

singlereplacem

entdo

uble

repl

acem

ent

A + B AB AB A + B

AB + C CB + A AB + CD AD + BC

H[A] + [B]OH [B][A] + H2O CxHx + O2 CO2 + H2Oheat

Types of Reactions

synthesisdecomposition

neutralization combustion

singlereplacem

entdo

uble

repl

acem

ent

A + B AB AB A + B

AB + C CB + A AB + CD AD + BC

H[A] + [B]OH [B][A] + H2O CxHx + O2 CO2 + H2Oheat

Combustion ReactionsThis is the combustion (burning) of a hydrocarbon (contains C and H) in oxygen Complete combustion results in the products water and carbon dioxide

CxHx O2+ CO2 + H2Oheat

hydrocarbon + oxygen carbon dioxide + water( ) (g) (g) (g)

Reactants Products

C 1 1

O 2 3

H 4 2

CH4 O2 CO2 + H2Oheat

methane + oxygen carbon dioxide + water(g) (g) (g) (g)

+eg

Combustion ReactionsThis is the combustion (burning) of a hydrocarbon (contains C and H) in oxygen Complete combustion results in the products water and carbon dioxide

CxHx O2+ CO2 + H2Oheat

hydrocarbon + oxygen carbon dioxide + water( ) (g) (g) (g)

Reactants Products

C 1 1

O 2 3 4

H 4 2 4

CH4 O2 CO2 + H2Oheat

methane + oxygen carbon dioxide + water(g) (g) (g) (g)

+eg

2

Combustion ReactionsThis is the combustion (burning) of a hydrocarbon (contains C and H) in oxygen Complete combustion results in the products water and carbon dioxide

CxHx O2+ CO2 + H2Oheat

hydrocarbon + oxygen carbon dioxide + water( ) (g) (g) (g)

Reactants Products

C 1 1

O 2 4 3 4

H 4 2 4

CH4 O2 CO2 + H2Oheat

methane + oxygen carbon dioxide + water(g) (g) (g) (g)

+eg

22

Combustion ReactionsA chemical reaction is taking place at the gas tap

C3H8 O2 CO2 + H2Oheat

propane + oxygen carbon dioxide + water(g) (g) (g) (g)

+

Which product of one of the reactions wersquove carried out already could be used to test if the condensation really is water

Is propane a covalent or ionic compound

Whatrsquos an alternative name for propane based on the naming conventions we have just learned

Combustion ReactionsA chemical reaction is taking place at the gas tap

Reactants Products

C

O

H

C3H8 O2 CO2 + H2Oheat

propane + oxygen carbon dioxide + water(g) (g) (g) (g)

+

Is it balanced

Combustion ReactionsA chemical reaction is taking place at the gas tap

Reactants Products

C 3 1

O 2 3

H 8 2

C3H8 O2 CO2 + H2Oheat

propane + oxygen carbon dioxide + water(g) (g) (g) (g)

+

Is it balanced

Combustion ReactionsA chemical reaction is taking place at the gas tap

Reactants Products

C 3 1 3

O 2 3 6

H 8 2

C3H8 O2 CO2 + H2Oheat

propane + oxygen carbon dioxide + water(g) (g) (g) (g)

+

Is it balanced

3

Combustion ReactionsA chemical reaction is taking place at the gas tap

Reactants Products

C 3 1 3

O 2 3 6 10

H 8 2 8

C3H8 O2 CO2 + H2Oheat

propane + oxygen carbon dioxide + water(g) (g) (g) (g)

+

Is it balanced

3 4

Combustion ReactionsA chemical reaction is taking place at the gas tap

Reactants Products

C 3 1 3

O 2 10 3 6 10

H 8 2 8

C3H8 O2 CO2 + H2Oheat

propane + oxygen carbon dioxide + water(g) (g) (g) (g)

+

Is it balanced

3 45

Combustion ReactionsAlcohols will also go through combustion reactions

httpwwwyoutubecomwatchv=SJCcH0ATMQ4

Do NOT try these at home

_CH3OH(l) + _O2(g) ___ (g) + ____ (g)methanol + oxygen

heat

carbon dioxide + water

Combustion ReactionsAlcohols will go through combustion reactions

Do NOT try these at home

_CH3OH(l) + _O2(g) _CO2(g) + _H2O(g)methanol + oxygen

heat

carbon dioxide + water

Reactants Products

C 1 1

O 3 3

H 4 2

Balance it

Combustion ReactionsAlcohols will go through combustion reactions

Do NOT try these at home

2CH3OH(l) + 3O2(g) 2CO2(g) + 4H2O(g)methanol + oxygen

heat

carbon dioxide + water

Reactants Products

C 1 2 1 2

O 3 8 3 8

H 4 8 2 8

Balance it

Types of Reactions

synthesisdecomposition

neutralization combustion

singlereplacem

entdo

uble

repl

acem

ent

A + B AB AB A + B

AB + C CB + A AB + CD AD + BC

H[A] + [B]OH [B][A] + H2O CxHx + O2 CO2 + H2Oheat

45

Single- amp double-replacement and neutralisation reactions

NaOHHCl amp

universal indicator HCl

AgNO3

Two white solids Which is PbNO3 and which is KI

Mg

CuSO4

Fe

HCl

NaHCO3

NaCl

H2O

Single Replacement ReactionsThese can be simplified as AB + C A + BCWhere an element trades places with another element in a compound

+ - + -+ +

hydrogen peroxide magnesium chloride + hydrogen(aq)(s)

Reactants Products

Cl

Mg

H

MgCl2 +HCl

balanced

(g)

Mg H2+

(aq)

Single Replacement ReactionsThese can be simplified as AB + C A + BCWhere an element trades places with another element in a compound

+ - + -+ +

hydrogen peroxide magnesium chloride + hydrogen(aq)(s)

Reactants Products

Cl

Mg

H

MgCl2 +HCl

balanced

(g)

Mg H2+

(aq)

Single Replacement ReactionsThese can be simplified as AB + C A + BCWhere an element trades places with another element in a compound

+ - + -+ +

hydrogen peroxide magnesium chloride + hydrogen(aq)

Reactants Products

Cl 1 2

Mg 1 1

H 1 2

MgCl2 +HCl

balanced

(g)

Mg H2+

(s)(aq)

Single Replacement ReactionsThese can be simplified as AB + C A + BCWhere an element trades places with another element in a compound

+ - + -+ +

hydrogen peroxide magnesium chloride + hydrogen(aq)

Reactants Products

Cl 1 2 2

Mg 1 1

H 1 2 2

MgCl2 +HCl

balanced

(g)

Mg H2+2

(s)(aq)

Types of Reactions

synthesisdecomposition

neutralization combustion

singlereplacem

entdo

uble

repl

acem

ent

A + B AB AB A + B

AB + C CB + A AB + CD AD + BC

H[A] + [B]OH [B][A] + H2O CxHx + O2 CO2 + H2Oheat

Double Replacement ReactionsThese can be simplified as AB + CD AD + CBWhere the anions and cations of two compounds trade places

+ - ++ -+ +

potassium iodide + lead nitrate potassium nitrate + lead iodide

(aq)(aq)

Reactants Products

K

I

Pb

NO3

+KI

balanced

(s)

Pb(NO3)2+

- - +

KNO3 PbI2(aq)

Nitrate is a polyatomic ion and must be kept together

Double Replacement ReactionsThese can be simplified as AB + CD AD + CBWhere the anions and cations of two compounds trade places

+ - ++ -+ +

potassium iodide + lead nitrate potassium nitrate + lead iodide

(aq)(aq)

Reactants Products

K 1 1

I 1 2

Pb 1 1

NO3 2 1

+KI

balanced

(s)

Pb(NO3)2+

- - +

KNO3 PbI2(aq)

Nitrate is a polyatomic ion and must be kept together

Double Replacement ReactionsThese can be simplified as AB + CD AD + CBWhere the anions and cations of two compounds trade places

+ - ++ -+ +

potassium iodide + lead nitrate potassium nitrate + lead iodide

(aq)(aq)

Reactants Products

K 1 1 2

I 1 2

Pb 1 1

NO3 2 1 2

+KI

balanced

(s)

Pb(NO3)2+

- - +

KNO3 PbI2(aq)

Nitrate is a polyatomic ion and must be kept together

2

Double Replacement ReactionsThese can be simplified as AB + CD AD + CBWhere the anions and cations of two compounds trade places

+ - ++ -+ +

potassium iodide + lead nitrate potassium nitrate + lead iodide

(aq)(aq)

Reactants Products

K 1 2 1 2

I 1 2 2

Pb 1 1

NO3 2 1 2

+KI

balanced

(s)

Pb(NO3)2+

- - +

KNO3 PbI2(aq)

Nitrate is a polyatomic ion and must be kept together

22

Letrsquos look at that againhellip

potassium iodide + lead nitrate potassium nitrate + lead iodide

(aq)(aq)+KI

(s)

Pb(NO3)2+ KNO3 PbI2(aq)

KWhich ions form

K+

Pb Pb2+

I I-

And the polyatomic ion

NO3

-

Letrsquos look at that againhellip

potassium iodide + lead nitrate potassium nitrate + lead iodide

(aq)(aq)+KI

(s)

Pb(NO3)2+ KNO3 PbI2(aq)

K+

Pb2+

I-

NO3

-

NO3

-

K+

NO3

-

Pb2+ I

-

I-

Reactants Products

K 1 1

I 1 2

Pb 1 1

NO3 2 1

The 2+ lead cation needs to be balanced by two single anions

The total number of atoms on each side are not balanced

Letrsquos look at that againhellip

potassium iodide + lead nitrate potassium nitrate + lead iodide

(aq)(aq)+KI

(s)

Pb(NO3)2+ KNO3 PbI2(aq)

22

K+

Pb2+

I-

NO3

-

NO3

-

K+

NO3

-

Pb2+ I

-

I-

K+

I-

K+

NO3

-

Reactants Products

K 1 2 1 2

I 1 2 2

Pb 1 1

NO3 2 1 2

Now they are

Types of Reactions

synthesisdecomposition

neutralization combustion

singlereplacem

entdo

uble

repl

acem

ent

A + B AB AB A + B

AB + C CB + A AB + CD AD + BC

H[A] + [B]OH [B][A] + H2O CxHx + O2 CO2 + H2Oheat

Neutralisation ReactionsThese can be simplified as HA + BOH H20 + BAWhere the acid (HA) is neutralized by the base (BOH) giving water and a salt (AB)

H[A] [B]OH+ [B][A] + H2O acid + base salt + water

(aq) (aq) (g) (g)

HCl NaOH+ NaCl + H2Ohydrochloric acid + sodium hydroxide sodium chloride + water

(aq) (aq) (aq) (g)

Reactants Products

Cl

Na

O

H

eg

These brackets donrsquot get used in equations ndash they are just there to show what is happening

Neutralisation ReactionsThese can be simplified as HA + BOH H20 + ABWhere the acid (HA) is neutralized by the base (BOH) giving water and a salt (BA)

H[A] [B]OH+ [B][A] + H2O acid + base salt + water

(aq) (aq) (g) (g)

HCl NaOH+ NaCl + H2Ohydrochloric acid + sodium hydroxide sodium chloride + water

(aq) (aq) (aq) (g)

Reactants Products

Cl 1 1

Na 1 1

O 1 1

H 2 2

eg

These brackets donrsquot get used in equations ndash they are just there to show what is happening

Types of Reactions

synthesisdecomposition

neutralization combustion

singlereplacem

entdo

uble

repl

acem

ent

A + B AB AB A + B

AB + C CB + A AB + CD AD + BC

H[A] + [B]OH [B][A] + H2O CxHx + O2 CO2 + H2Oheat

Balancing Equation PracticeNow try the activities on this PhET simulation to

help practice balancing equations

httpphetcoloradoeduensimulationbalancing-chemical-equations

1 Complete the introduction stage 2 Some of the examples are on the sheet 3 Try the challenge quizzes

Classify and balance thesehellip

C6H12O6 O2+ CO2 + H2Oheat

glucose + oxygen carbon dioxide + water(s) (g) (g) (g)

Cell respiration

Housekeeping classToday we need to make sure everyone is up to date on all work and can understand balancing and reactions

1 Check all One World work has been submitted 2 Check in with incomplete elements task people3 Work through last weekrsquos reactions and balance them 4 Turn these sheets back in to be checked again

If you have completed everything and are all up to date you canbull practice balancing and naming using the resources on the GoogleSitebull Find out more about the lsquoMolersquo and stoichiometry

MrTrsquos promisebull All Chem work will be checked and graded by Thursdaybull If you performed poorly in One World you can do another essay or

article in your own time Due 16 Jan at the very latest

For more resources

This is a Creative Commons presentation It may be linked and embedded but not sold or re-hosted

Please consider a donation to charity via Biology4GoodClick here for more information about Biology4Good charity donations