Chemical Reactions

Spring 2015

I. Describing Chemical ChangeA. Writing Chemical Equations

1. A chemical reaction is the process by which one or more substances are changed into one or more different substances.2. A chemical equation represents a chemical reaction.3. A correct chemical equation shows what changes take place and the relative amounts of the various elements and compounds involved in the reaction.4. The original substances in the reaction are called the reactants.5. The substances that are formed in the reactions are the products.a. Example: Iron + Oxygen —> Iron (II) Oxideb. Example: Hydrogen + Oxygen —>Water6. The —> means yields, gives, or reacts with to produce.

Examples of Chemical Reactions

I.Describing Chemical ChangeB. Chemical Equations

1. To shorten an equation, we use chemical formulas to write chemical equations.2. In a chemical equation, the —> separates the reactant and the products.3. A skeleton equation show just the formulas for the reactants and products.4. A catalyst is added to a reaction to speed up the reaction.5. A catalyst is neither a product or a reactant so it is written over the —>.

Symbols Used in Chemical Equations

Create flash cards. Quiz over the symbols on Wednesday

I. Describing Chemical Change C. Balancing Chemical Equations 1. An equation that does not indicate the

quantity of the reactants needed to make the product is called an unbalanced equation.2. To balance the equation, the same number of elements on both sides of the equation.3. Use coefficients to balance the formulas.4. You can not change the subscripts in the formula.

H2 N2 F2 O2 I2 Cl2 Br2

No Fear of Having Iced Chocolate Brownies!-An acronym to remember the 7 diatomic elements-

Diatomic Molecules

Balancing EquationsThe number and type of all atoms must be the same in the reactants and products.

You can generally balance in the order of MINOH:

Metals Polyatomic Ions Nonmetals Oxygen Hydrogen

1. Write the symbol that fits the meaning

  Separates 2 reactants or products +

“yields” or “produces” indicates result of a reaction A reactant or product in the solid state  A reactant or product in the liquid state A reactant or product in aqueous solution (dissolved in water) A reactant or product in the gaseous state

Meaning Symbol

3 minutes

Balance the following equations

1. __NaCl + __BeF2 --> __NaF + __BeCl2

2. __FeCl3 + __Be3(PO4)2 --> __BeCl2 + __FePO4

3. __AgNO3 + __LiOH --> __AgOH + __LiNO3

Remember:Check for diatomic gasesWatch for PolyatomicsBalance Oxidation NumbersDo not forget to use “MINOH”

7 minutes

Balance the following equations

4. __ Pb(NO3)2 + __ KI ---> __ PbI2 + __ KNO3

5. __Mg + __Mn2O3 --> __MgO + __Mn

6. calcium plus fluorine yields calcium fluoride.

7 minutes

Remember:Check for diatomic gasesWatch for PolyatomicsBalance Oxidation NumbersDo not forget to use “MINOH”

2. In the chemical equation below, identify the reactants, products, subscripts, & coefficients

4 Fe(s) + 3 O2(g) → 2 Fe2O3(s)

a. What are the reactant(s)?

  b. What is the coefficient for Iron?

c. What are the product(s)?    d. # of moles of O2 =   e. # of atoms of Fe in 2 Fe2O3 =

  f. Which reactants are solid(s)?=

3. Balance a chemical equation by changing coefficients/subscripts (choose one)

3 minutes

II. Types of Chemical ReactionsA. Classifying Chemical Reactions

1. There are five types of chemical reactionsa. Synthesisb. Decompositionc. Single Displacementd. Double Displacemente. Combustion

2. Sometimes a reaction can fit into more than one class of reaction.

II. Types of Chemical Reactions B. Combination Reactions

1. Combination (Synthesis) reaction occur when two or more substances combine to form one new substance.2. The product of a combination reaction is always a compound.3. Combination can be either element or compounds.

a. element + element —> compoundb. compound + compound —>

compound Example: 2H2 + O2 —> 2H2O

II. Types of Chemical Reactions C. Decomposition Reactions

1. Decomposition reaction occur when substances breaks up into simpler substances.

a. compound —> two or more compounds or elements

b. Example: 2KClO3 —> 2KCl + 3O22. Most decompositions require energy in the form of heat, electricity, or light.3. Extreme decomposition reactions that produce gaseous products and heat are often the cause of explosions.

II. Types of Chemical Reactions D. Single Replacement Reactions

1. Single displacement reaction occur when one element displace another in a compound.

a. element + compound —> element + compound

b. Example: Cl2 + 2KBr —> 2KCl + Br22. In compounds metals will replace another metal based on the activity of the single metal.3. Nonmetals can replace another nonmetal from a compound.

II. Types of Chemical Reactions E. Double Replacement Reactions

1. Double displacement reaction occur when an element in a compound trades place with another element in another compounds.

a. compound + compound —> compound + compound

b. Example: NaOH+ HCl —>NaCl + HOH (H2O)2. Double Replacement reactions occur mainly between ionic compounds.3. The products can be a precipitate (solid), a gas, or water.

II. Types of Chemical Reactions F. Combustion Reactions

1. Combustion occurs when a substance, usually a hydrocarbon, burn in the presence of oxygen.

a. hydrocarbon + oxygen —> carbon dioxide + water

b. Example: CH4 + 2O2 —> CO2 +2H2O2. For any clean combustion reaction, the products will always be carbon dioxide (CO2) and water.

II. Types of Chemical ReactionsG. Predicting Product of Chemical Reactions 1. To predict the product of a

reaction, you must determine which type of reaction is occurring.2. Not all reactions fall into the five classes of reactions.

III. Reactions in Aqueous SolutionsA. Net Ionic Equations

1. An aqueous solution is a compound dissolved in water.2. For reaction taking place in water, it is customary to write equation in ionic form (ions taking part in the reaction, not spectators ions).3. Ions that are not directly involved in a reaction are called spectator ions.4. A complete ionic equation show all the ions as free ions.5. Spectator ions appear on both sides of the equation.6. You can rewrite the equation leaving out the spectator ion which is called the net ionic equation. 7. In writing balanced net ionic equations, you must also balance the ionic charge to zero.8. Use coefficients to balance the net ionic equation.

III. Reactions in Aqueous SolutionsB. Predicting the Formation of a Precipitate

1. Mixing of two aqueous solutions can result in the formation of an insoluble salt called a precipitate.2. The formation of the precipitate is predicted by the using the general solubility rules.

Synthesis

Decomposition

Combustion

Single Replacement

Double Replacement

One reactant

anything + oxygen

Could be synthesis

element + ionic compound

ionic compound + ionic compound

Not on of the other types of reactions…

Predicting ProductsNext slide

Break it down one step

hydrocarbon + O2 CO2 + H2O

Check activity! Ion swap

Check solubility!

Ion swap

SynthesisSimple

Specific

metal + nonmetal

nonmetal(s) + nonmetal

ionic compound

simplest compound

metal oxide + water metal hydroxide

metal oxide + nonmetal oxide ionic compound

nonmetal oxide + water oxyacid

1. Synthesis

Example C + O2 CO2

OO C + O O C

General: A + B AB

Ex. Synthesis Reaction

Practice Predict the products.

Na(s) + Cl2(g)

Mg(s) + F2(g)

Al(s) + F2(g)

Synthesis: A synthesis reaction is when two or more simple compounds combine to form a more complicated one.

Practice

Predict the products.

Na(s) + Cl2(g)

Mg(s) + F2(g)

Al(s) + F2(g)

NaCl(s)

MgF2(s)

AlF3(s)

Now, balance them.

2. Decomposition

Example: NaCl Na + Cl2

General: AB A + B

Cl Na Cl + Na

Practice

Decomposition: A decomposition reaction is the opposite of a synthesis reaction - a complex molecule breaks down to make simpler ones.

B2O3

AlCl3

Ex. Decomposition Reaction

3. Single DisplacementExample: Zn + CuCl2 ZnCl2 + Cu

ZnClCl Cu +

General: AB + C AC + B

ClCl Zn Cu+

Zn was oxidizedWent from neutral (0) to (+2)

Cu was reducedWent from (+2) to Neutral (0)

Ex. Single Replacement Reaction

Single Replacement ReactionsWrite and balance the following single

replacement reaction equation:

Zn(s) + HCl(aq)

• Single Replacement: This is when one

element trades places with another element in a compound.

Cu(s)+ Al(NO3)3(aq)

Single-Replacement Reactions

FeCl2 + Cu

MgBr2 + Cl2

“Magic blue-earth”

Zinc in nitric acid

A + BC AC + B

General Form

Zn(NO3)2 + H2

Can Fe replace Cu? Yes

LiRbKBaCaNaMgAlMnZnCrFeNiSnPbH2

CuHgAgPtAu

F2

Cl2Br2

I2

Can Zn replace H? Yes

Can Br replace Cl? No

NO REACTION

Fe + CuCl2

Zn + 2HNO3

MgCl2 + Br2

Activity Series

Halogen Reactivity

Ca

Activity Series

Foiled again –Aluminum loses to Calcium

Element Reactivity

LiRbKBaCaNaMgAlMnZnCrFeNiSnPbH2

CuHgAgPtAu

Halogen Reactivity

F2

Cl2Br2

I2

Mg + AlCl3

Al + MgCl2

Predict if these reactions will occur

Al + MgCl2

Can magnesium replace aluminum?

Activity Series

YES, magnesium is more reactive than aluminum.

2 23 3

Can aluminum replace magnesium?

Activity Series

NO, aluminum is less reactive than magnesium.

Therefore, no reaction will occur.

No reaction

MgCl2 + Al No reaction

The question we must ask is can the single element replace its counterpart? metal replaces metal or nonmetal replaces nonmetal.

Order of reactants DOES NOT

determine how they react.

Single Replacement ReactionsWrite and balance the following single

replacement reaction equation:

Zn(s) + HCl(aq) ZnCl2 + H2(g)

• NaCl(s) + F2(g) NaF(s) + Cl2(g)

• Al(s)+ Cu(NO3)2(aq) Cu(s)+ Al(NO3)3(aq)

4. Double displacement

Example: MgO + CaS MgS + CaO

General: AB + CD AD + CB

SOMg Ca+

O S

Mg Ca+

Double Replacement Reactions Think about it like “foil”ing in algebra, first

and last ions go together + inside ions go together

Example: AgNO3(aq) + NaCl(s) AgCl(s) + NaNO3(aq)

Another example:

K2SO4(aq) + Ba(NO3)2(aq) KNO3(aq) + BaSO4(s)

TABLE OF SOLUBILITIES IN WATER

aluminum ss s n s n i s s i s dammonium s s s s s s s s s s s

barium s s i s i s s s i i dcalcium s s i s s ss s s i ss d

copper (II) s s i s i i n s i s iiron (II) s s i s n i s s i s iiron (III) s s n s i i n s i ss d

lead s ss i ss i i ss s i i imagnesium s s i s s i s s i s dmercury (I) ss i i i ss n i s i ss imercury (II) s ss i s ss i i s i d ipotassium s s s s s s s s s s s

silver ss i i i ss n i s i ss isodium s s s s s s s s s s s

zinc s s i s s i s s i s i

acet

ate

brom

ide

carb

onat

e

chlo

ride

chro

mat

e

hydr

oxid

e

iodi

de

nitra

te

phos

phat

e

sulfa

te

sulfi

de

i = insolubless = slightly solubles = solubled = decomposesn = not isolated

Legend

Solubility Rules

1. Most nitrates are soluble.

2. Most salts containing Group I ion and ammonium ion, NH4+, are soluble.

3. Most chloride, bromide, and iodide salts are soluble, except Ag+, Pb2+ and Hg2

2+.

4. Most sulfate salts are soluble, except BaSO4, PbSO4, Hg2SO4, and CaSO4.

5. Most hydroxides except Group 1 and Ba(OH)2, Sr(OH)2, and Ca(OH)2 are only slightly soluble.

6. Most sulfides, carbonates, chromates, and phosphates are only slightly soluble.

Practice-Double Replacement reactions Predict the products. 1. HCl(aq) + AgNO3(aq) 2. CaCl2(aq) + Na3PO4(aq) 3. Pb(NO3)2(aq) + BaCl2(aq) 4. FeCl3(aq) + NaOH(aq) 5. H2SO4(aq) + NaOH(aq) 6. KOH(aq) + CuSO4(aq)

Double Replacement: This is when the anions and cations of two different molecules switch places, forming two entirely different compounds.

Neutralization reactions Also known as Acid-base: This is a special kind of

double displacement reaction that takes place when an acid and base react with each other. The H+ ion in the acid reacts with the OH- ion in the base, causing the formation of water. Generally, the product of this reaction is some ionic salt and water:

HA + BOH ---> H2O + BA One example of an acid-base reaction is the reaction of

hydrobromic acid (HBr) with sodium hydroxide:

HBr + NaOH ---> NaBr + H2O

Acid + base ---> salt + water

5. Combustion Reactions Combustion reactions

- a hydrocarbon reacts with oxygen gas.

This is also called burning!!!

In order to burn something you need the 3 things in the “fire triangle”:

1) Fuel (hydrocarbon) 2) Oxygen

3) Something to ignite the

reaction (spark)

Combustion Reactions In general:

CxHy + O2 CO2 + H2O Products are ALWAYS carbon dioxide and water.

(although incomplete burning does cause some by-products like carbon monoxide)

Combustion is used to heat homes and run automobiles (octane, as in gasoline, is C8H18)

You can generally balance Combustion reactions in the order of CHO:

CarbonHydrogenOxygen

Combustion reactions are harder to balance than any otherReactions.

Combustion Example C5H12 + O2 CO2 + H2O

Write the products and balance the following combustion reaction:

C10H22 + O2

Combustion: A combustion reaction is when oxygen combines with another compound to form water and carbon dioxide. These reactions are exothermic, meaning they produce heat.

Mixed PracticeState the type & predict the products.

1. BaCl2 + H2SO4 2. C6H12 + O2 3. Zn + CuSO4 4. Cs + Br2 5. FeCO3

Redox reactions - transfer of electrons between species.

All the redox reactions have two parts:

Oxidation Reduction

Oxidation-Reduction reactions

Oxidation–Reduction Reactions or redoxInvolves 2 processes:Oxidation = Loss of Electrons (LEO)

Na Na+ + e Oxidation Half-Reaction

Reduction = Gain of electrons (GER)Cl2 + 2e 2Cl Reduction Half-Reaction

Net reaction: 2Na + Cl2 2Na+ + 2Cl

› Oxidation & reduction always occur together› Can't have one without the other

Your Turn!

Which species is being oxidized in the following oxidation-reduction reaction?

Zn(s) + Pt2+(aq) Pt(s) + Zn2+(aq)A. Pt(s)B. Zn2+(aq)C. Pt2+(aq)D. Zn(s)E. None of these, as this is not a redox reaction.

Hierarchy of Rules for Assigning Oxidation Numbers

1. Oxidation numbers must add up to charge on molecule, formula unit or ion.

2. Atoms of free elements have oxidation numbers of zero.

3. Metals in Groups 1A, 2A, and Al have +1, +2, and +3 oxidation numbers, respectively.

4. H & F in compounds have +1 & –1 oxidation numbers, respectively.

5. Oxygen has –2 oxidation number in all compounds but peroxides

Ex. Assigning Oxidation Number1. Li2O

Li (2 atoms) × (+1) = +2 (Rule 3)O (1 atom) × (–2) = –2 (Rule 5) sum = 0 (Rule 1)+2 –2 = 0 so the charges are balanced to zero

2. CO2 C (1 atom) × (x) = xO (2 atoms) × (–2) = –4 (Rule 5) sum = 0 (Rule 1)x 4 = 0 or x = +4C is in +4 oxidation state

Redefine Oxidation-Reduction in Terms of Oxidation Number

A redox reaction occurs when there is a change in oxidation number.

Oxidation › Increase in oxidation number› e loss

Reduction› Decrease in oxidation number› e gain

Using Oxidation Numbers to Recognize Redox Reactions

Sometimes electron transferred in "formal" sense.

2H2O2O2+ +-4 +40+1 -2 +1 -2

C: increase oxidation

O: decrease reduction

CH4 CO2O: oxidation number decreases by 2

reductionC: oxidation number increases by 8

oxidation

Oxidation-Reduction reactions Identifying Reaction Types

A redox reaction must involve a change in oxidation number for two of the elements involved in the reaction. The oxidized element increases in oxidation number, while the reduced element decreases in oxidation number.

Single-replacement reactions are redox reactions because two different elements appear as free element (oxidation number of zero) on one side of the equation and as part of a compound on the other side. Therefore, its oxidation number must change.

Zn is oxidized from Zn0 to Zn2+  and the H is reduced from H+ to H0

Combustion reactions are redox reactions because elemental oxygen (O 2 ) acts as the oxidizing agent and is itself reduced.

Most combination and decomposition reactions are redox reactions since elements are usually transformed into compounds and vice-versa. The thermite reaction involves ferric oxide and metallic aluminum:

Oxidation-Reduction reactions So what types of reactions are not redox reactions? Double-

replacement reactions such as the one below are not redox reactions because ions are simply recombined without any transfer of electrons.

Note that the oxidation numbers for each element remain unchanged in the reaction.

Acid-base reactions involve a transfer of a hydrogen ion instead of an electron. Acid-base reactions, like the one below, are also not redox reactions.

Again, the transfer of an H + ion leaves the oxidation numbers unaffected. In summary, redox reactions can always be recognized by a change in oxidation number of two of the atoms in the reaction. Any reaction in which no oxidation numbers change is not a redox reaction.

Why is the Zn + HCl reaction a redox reaction?

Why is the sodium sulfate + barium nitrate reaction not a redox reaction?

Does the transfer of H + affect oxidation numbers?

EXIT TICKET

1) ____ NaBr + ____ Ca(OH)2 ___ CaBr2 + ____

NaOH

Type of reaction: _____________________________

2) ____ Pb + ____ H3PO4 ____ H2 + ____ Pb3(PO4)2 

Type of reaction: _____________________________

3) lithium nitride is mixed with ammonium nitrate.

lithium nitrate and ammonium nitride are produced.

Type of reaction: _____________________________

EXIT TICKET

For the following equations predict the products, balance and identify the type of reaction.

______2. ____Na2CO3 + ____CuCl2 _______ + _______

______1. ____ Na + ____ MgBr2 ________ + _______

EXIT TICKET

Type of reaction:_____________________________

Type of reaction:_____________________________

Remember:Check for diatomic gasesWatch for PolyatomicsBalance Oxidation NumbersDo not forget to use “MINOH”

Guide to Chemical Reactions

Social Media style

Synthesis Reaction or the Hook Up

Brad Pitts + Angelina Jolie

Beyonce + Jay-z

Ashton Kutcher and Mila Kunis

Will + Jada

George Clooney + Amal Alamuddin

Kim K + Kanye

A + B = AB

Decomposition or the Big Breakup

Taylor Swift dumps ???????

Ashton Kutcher dumps Demi Moore

Chris Rock dumps his wife

Kevin Hart dumps his wife

Khloe K dumps Lamar Odom

•AB = A + B

Single Displacement Reaction or the Swap

Brad/Jennifer + Angelina = Brangelina + Jennifer out in the cold

J-Low/Marc Anthony + Casper Smart =J-Low/Casper Smart + Marc Anthony out in the cold

AB + C = AC + B

AB + C* = A + BC*

Double Displacement or the SwitchRapper T’Pain/ GFA + Rapper Lil Wanye / GFB Switch and become

Rapper T’Pain/GFB + Rapper Lil Wanye/GFA

TI and Tiny + Future and Ciara Switch and become TI and Ciara + Future and Tiny ™

AB + CD = AD + CB

Combustion

Amanda Bynes, Charlie Sheen, Amy Winehouse and Lindsey Lohan

One big “hot” toxic flammable mess