chemical reactions and equations types of reactions

Chemical Reactions and Equations

Types of Reactions

Predicting Products

Activity Series

Identifying Oxidation-Reduction

Reactions

A preview of things we will do

Chemical Reactions are AWESOME!

https://www.youtube.com/watch?v=0Bt6RPP2ANI

Characteristics of Chemical Reactions

A chemical reaction: is a process in which the chemical and physicalproperties of the original substance changes

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and new substances with differentphysical and chemical properties are formed.

PIZZA!!!

https://www.youtube.com/watch?v=tOkCgAwhh9U

Chemical Equations

A chemical equation has two

parts:

• reactants: the starting materials

• products: the substances

formed in the reaction (ending)

example: C + O2 CO2reactants products

Identifying Reactants and Products

Identify the reactants and products in the following equation:

2Al(s) + 3Cl2(g) → 2AlCl3(s)

reactant(s)

products(s)

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Al, Cl2

AlCl3

Reaction SymbolsYields or Produces

Solid or precipitate (s) or

Liquid (l)

Gas (g) or

Aqueous (acids & bases) (aq)

Catalyst (speeds up) Ni

Heat Added

Reversible Reaction ⇄

Identifying parts of a Chemical Equation:

1. Which are the reactants?

2. Which are the products?

3. Which are the coefficients?

4. Which is the subscript?

2 Mg + O2 2 MgO

Reactants Products

Mg + O2

MgO

# in front

# on bottom

SRIRACHA!!!

https://www.youtube.com/watch?v=U2DJN0gnuI8

Indications of a Chemical Reaction

1. Production of a gas.

2. Formation of a precipitate. (a solid that forms from two liquids)

3. Change in energy.

Endothermic reaction – energy is absorbed

Exothermic Reaction – energy is released

4. Change in color or odor.

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Why wet dogs stink!!!

https://www.youtube.com/watch?v=X9AozZLZnCU

Law of Conservation of Mass

Chemical equations are balanced to satisfy the Law of Conservation of Mass

The Law of Conservation of Mass states: mass cannot be created or destroyed by ordinary physical or chemical means.

total mass of the reactants must equal the total mass of the products.

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-Mass is neither created nor destroyed!

The number of atoms (and total mass) on the reactant side

must equal the number of atoms (and total mass) on the

product side.

1CH4 + 2O2 1CO2 + 2H2O16 g + 64 g = 44 g + 36 g

80 g = 80 g

Example: In a chemical reaction, 4 g of hydrogen combine with 32 g of oxygen to form water (2H2 + O2 2H2O). What is the mass of the product formed?

Answer: Reactants = Products

4 g + 32 g = 36 g H2O

Remember: Calculate formula mass.

(1 C x 12) + (4 H x 1) =

16 g

Practice:1. In a chemical reaction, 4 g of hydrogen combine with 32

g of oxygen to form water What is the mass of the product formed?

2H2 + O2 2H2O

2. If 60 g of ethane burns in 224 g of oxygen to produce 108 g

of water, what is the mass of the remaining product?

C2H6 + O2 CO2 + H2O

4 g + 32 g = ? g

60 g + 224 g = ? g + 108 g 176 g

36 g

Homework/Do NOW:

Conservation of Mass Practice Problems (12 questions)

Due FRIDAY 1/29/16

Turn it in today if you finish!

Warm-Up: Answer the following

1. What are the two parts of a chemical equation?

2. What is the law of conservation of mass?

3. According to the law, what must be equal on both sides of the equation? (hint: there are TWO things that must be equal (the total number of _______ and the total ________ in grams)


Remember that atoms don’t

change in a chemical reaction;

they just rearrange.

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For a chemical equation to accurately

represent a reaction, the same number of

each kind of atom must be on the left side of

the arrow as are on the right side.

Counting Atoms in Chemical Compounds

Before we can balance an equation, we must first make

sure that everyone can count the atoms present in a

compound. Here are some examples.

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KClO3 ___K, ___Cl, ___O

Mg(OH)2 ___Mg, ___O, ___H

Al2(SO4)3 ___Al, ___S, ___O

2Al(NO3)3 ___Al, ___N, ___O

1 1 3

1 2 2

2 3 12

2 6 18

You Try It

Determine the number of each atom present

in each of the following.

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AlPO3 ___Al, ___P, ___O

Ba(NO3)2 ___Ba, ___N, ___O

HC2H3O2 ___H, ___C, ___O

3Fe3(PO4)2 ___Fe, ___P, ___O

1 1 3

1 2 6

4 2 2

9 6 24

Identifying Balanced Chemical Equations

An equation in which the number of atoms of

each element is the same on both sides of

the equation is called a balanced chemical

equation.

Pb(NO3)2 + 2KI → PbI2 + 2KNO3

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Reactant Side Element Product Side

Pb

N

O

K

I

1 12 26 6

2 22 2

You try it: Handout

Balancing Practice I

Worksheet

15 minutes. GO!

Balancing Chemical Equations

Example:

Mg + HCl → MgCl2 + H2

What coefficient must be added in front of

HCl in order to balance the chlorine and the

hydrogen?

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2

Ex. 1: Mg + HCl MgCl2 + H2

Ex. 2: KClO3 − KCl + O2

1 Mg 1 Mg1 H 2 H

2

1 K

1 Cl

3 O

2

1 Cl

2

2 Cl

3

2 H

2 Cl

1 1 1

1 K

1 Cl

2 K

2 Cl

6 O

2 O2 K

2 Cl

6 O

Writing Balanced Chemical Equations

If the skeleton equation is not written for you,

you must write your own.

Example** When an electric current is passed

through water, the water molecules break

down to produce hydrogen and oxygen.

Bubbles of each gas are evidence of the

reaction.

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→ H2(g)H2O(l) + O2(g)2 2

You Try It

Write a balanced equation for each of the

following reactions.

**When magnesium metal and oxygen gas

react, the product is solid magnesium

oxide.

**When nitrogen and hydrogen gas react, the

product is ammonia gas.

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N2(g) + H2(g) → NH3(g)

2Mg(s) + O2(g) → MgO(s)

3 2

2

→ BaSO4(s)Al2(SO4)3(aq) + BaCl2(aq)

+ AlCl3(aq)

Challenge: **Writing Balanced Chemical Equations

Example 2. Solutions of aluminum sulfate

and barium chloride react to produce solid

barium sulfate and aqueous aluminum

chloride.

aluminum sulfate = Al3+, SO42- = Al2(SO4)3

barium chloride = Ba2+, Cl- = BaCl2

barium sulfate = Ba2+, SO42- = BaSO4

aluminum chloride = Al3+, Cl- = AlCl3

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2

33

Write a balanced equation for each of the

following reactions.

**Aluminum metal reacts with oxygen gas to

produce solid aluminum oxide.

**Solutions of calcium chloride and sodium

sulfate react to produce aqueous sodium

chloride and solid calcium sulfate.

Al(s) + O2(g) → Al2O3(s)

You Try It

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CaCl2(aq) + Na2SO4(aq)→ NaCl(aq) + CaSO4(s)

2

2

4 3

Homework/DO NOW:

14 practice problems TO BE TURNED IN when completed

[[you need a computer]]

www.socrative.com

Room code: KILBANESTP

Enter your name

http://www.socrative.com/

1. Synthesis

A + B AB

2. Decomposition

AB A + B

3. Single Replacement

A + BC B + AC

4. Double Replacement

AB + CD CB + AD

5. Combustion Reaction

CxHy + O2 CO2 + H2O

Types of Reactions

Synthesis (Combination) Reactions

two substances – either elements or

compounds – combine to form a single

compound.

The general equation for a synthesis reaction is:

A + B → C

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Practice: Synthesis ReactionsWrite the product and balance the equation.

Remember, if you have a metal + nonmetal, you have to balance the charges!!!

1) H2 + O2

2) Zn + S

3) H2 + Cl2

4) K(s) + Cl2 (g)

5) N2 + H2

H2O

ZnS

HCl

NH3

KCl

2 2

2

2

3 2

2

Balanced

“ammonia”

Zn2+ S2- Zn2+ S2-

H+ Cl- H+ Cl-

K+ Cl- K+ Cl-

II. Decomposition Reaction: A compound breaks down into simpler products.

AB A + B

HgO Hg + O22 2

Diatomic

Metal Carbonates: break down into the

metal oxide and carbon dioxide.

CaCO3

Na2CO3

PbCO3

CaO + CO2

Na2O + CO2

PbO + CO2

Ca2+ O2-

Na+ O2-

Pb2+ O2-

III. Single Replacement ReactionOne element replaces another element.

Remember: The positive ion always goes with the negative ion!

A + BC B + AC

A) Metal replaces Metal

Cu + AgNO3

B) Nonmetal replaces Nonmetal

Br2 + KI

Cu(NO3)2 + Ag

KBr + I2

Cu2+ Ag+ NO31- Cu2+ NO3

1- Ag +

Pos. ion goes with neg. ion!

Br1- K+ I1- K+ Br1- I1-

Diatomic

Solutions of ionic compounds trade ions

Outside two go together; Inside two go

together. (+ion with ion)

AB + CD CB + AD

Double Replacement

Double-Replacement Reactions

KBr + NaCl → KCl + NaBr

MgCl2 + 2LiF → MgF2 + 2LiCl

HCl + NaOH → NaCl + H2O

(This is an example of a special type of double-replacement

reaction known as an acid-base neutralization reaction.)


Combustion Reactions A burning of a hydrocarbon compound in oxygen

produces carbon dioxide and water.

CxHy + O2 (g) CO2 + H2O

Complete Combustion Reactions

CH4 + 2O2 → CO2 + 2H2O

2C3H7OH + 9O2 → 6CO2 + 8H2O


Welcome to FRIDAY!Make sure you picked up the handout by the door.

Practice Sheet: your options…Single replacement

Double replacement

Synthesis

Decomposition

Acid-base neutralization

Combustion

YOU HAVE 10 MINUTES. MAY THE ODDS BE EVER IN YOUR FAVOR

35 minutes of PUTTING IT TOGETHER:Complete and balance the following equations. Label

the type of reaction.

1. HgO

2. C5H10 + O2

3. AgNO3 + NaCl

4. Li + N2

5. K + Ba(C2H3O2)2

6. H2O

7. Mg(NO3)2 + KOH

8. C6H14 + O2

9. Al + S

10. F2 + AlCl3

Decomposition2 Hg + O22

CombustionCO2 + H2O2 10 1015

Double-ReplacementAgCl + NaNO3

SynthesisLi3N26

Single-ReplacementKC2H3O2 + Ba2 2

DecompositionH2 + O22 2

Double-ReplacementMg(OH)2 + KNO322

CombustionCO2 + H2O2 12 1419

SynthesisAl2S32 3

Single-ReplacementAlF3 + Cl23 22 3Back to main menu

Activity Series

Not all single-replacement reactions will occur.

Mg + ZnCl2

Zn + MgCl2

How can you determine if a single-replacement

reaction will occur or not?

MgCl2 + Zn

No Reaction

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Whether or not a single-

replacement reaction will

occur can be determined

by using an activity series.

The activity series of

metals lists metals in order

of chemical reactivity.

A reactive metal will

replace any metal found

below it in the activity

series.

Activity Series of Metals

WRITE THIS DOWN!

The halogens can also take

place in single-replacement

reactions.

The order of reactivity for the

halogens from highest to

lowest reactivity: is fluorine,

chlorine, bromine, iodine.

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Activity of

Halogens

F2

Cl2Br2

I2

Activity Series of Halogens

Activity of

Halogens

F2

Cl2Br2

I2

Incr

easi

ng

act

ivit

y

Will the first element replace

the second?

1.Mg Ag

2.BrF

3.PbCu

4.ClI

Yes

No

Yes

Yes

Single-Replacement Reactions

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Remember: In order to replace an

element, the first element (reactant)

has to be HIGHER on the activity

series then the second

Use the activity series to determine whether or not the following

reactions will occur. If the reaction will occur spontaneously,

complete and balance the reaction. If it does not occur, write “no

reaction”.

1. Zn + Na2O →

2. Li + AgNO3 →

3. Fe + CuSO4 →

4. Cl2 + KBr

Ag + LiNO3

Cu + FeSO4

No Reaction

Single-Replacement Reactions

KCl + Br22 2

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The equation says “no reaction”, plus the picture shows that nothing

is happening. That must mean WHAT?

The metal ion originally in the solution is MORE reactive (higher on

the activity series list) then the metal that was dropped into the

solution. You could also say that the metal dropped into the

solution was lower on the list than the original metal.

In order to replace hydrogen, the

unknown element must be ABOVE the

known element. Nickel is the only

metal listed that is above Hydrogen on

the list (gold is below)

I need you to FOCUS today!

We have a LOT to do!!!

Please make sure you have the pink half sheet

Oxidation-Reduction Reactions (Redox)

Oxidation-Reduction reactions

occur when electrons are

transferred between reactions.

Examples include: the burning of

gasoline and the rusting of a nail.

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OxidationOxidation originally meant the combination of an

element with oxygen to give oxides.

However, today it is defined as:

the loss of electrons.

(Oxygen does not have to be present for oxidation

to occur.)

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ReductionReduction originally meant the loss of oxygen from

a compound.

Today it is defined as:

the gain of electrons.

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Helpful Mnemonics

Leo the Lion says Ger

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L – Loss

e – of electrons

o – is oxidation

G – Gain

e – of electrons

r – is reduction

Helpful Mnemonics

OIL RIG

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O – Oxidation

I – Is

L – LOSS

R – Reduction

I – Is

G – Gain

TIPS for Assigning Oxidation Numbers

1. The oxidation number of a

monatomic ion (by itself) is

equal to its given charge.

Examples:

Br- equals

Fe3+ equals

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-1

+3

Rules for Assigning Oxidation Numbers

2. For a polyatomic ion, the sum

of the oxidation numbers must

equal the ionic charge of the

ion.

Examples:

SO42- equals

NO3- equals

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-2

-1


3. The oxidation number of a

metal cation is the same as its

ionic charge.

Examples:

sodium ion is

calcium ion is

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+1

+2


4. The oxidation number of

hydrogen in a compound is

usually +1.

Exception: In metal hydrides,

(ex. NaH) hydrogen is -1.

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5. The oxidation number of

oxygen in a compound is

usually -2

Exception: In peroxides (ex.

H2O2) oxygen is -1.

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6. The oxidation number of an

uncombined element is 0.

For example, the oxidation number of

the potassium atoms in potassium

metal, K, and of the nitrogen atoms in

nitrogen gas, N2, is zero.

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7. For any neutral compound, the

sum of the oxidation numbers

of the atoms in the compound

must equal 0.

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When assigning oxidation numbers to the

elements in neutral compound or ion (positive +

negative), assign them in the following order:

1.Lone elements (not in a compound): 0

2.metal –

3.hydrogen –

4.oxygen –

5.everything that is left over

use the charge from the periodic table

+1 (or -1 in metal hydrides)

-2 (or -1 in peroxides)


1. What is the oxidation number of each element in the following?

SO2

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+4 -2

-4+4 =0

S = +4

O= -2


KClO3

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+1 -2

-6+1 =0

K = +1

O= -2

Cl = +5+5

+5


KClO2

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+1 -2

-4+1 =0

K = +1

O= -2

Cl = +3+3

+3


CO32-

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+4 -2

-6+4 = -2

C = +4

O= -2

You Try It. Determine the oxidation number of each element in each of the following on your own.

5. Na2Cr2O7 Na = Cr = O=

6. BaH2 Ba = H =

(Hint: BaH2 is a metal hydride.)

7. Li2O2 Li = O =

(Hint: Li2O2 is a peroxide.)

8. ClO3- Cl = O =

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+2

+6 -2+1

-1

+1 -1

+5 -2

Oxidation Number Changes

The changes in oxidation number can be

used to determine which elements are

oxidized and which elements are reduced.

Remember – an increase in the oxidation

number of an atom signifies oxidation and a

decrease in the oxidation number signifies

reduction.

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Oxidation Number ChangesUse the change in oxidation number to

identify which elements are oxidized and

reduced in each of these reactions.

1. F2(g) + 2HBr(aq) → 2HF(aq) + Br2(l)

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0 +1 -1 +1 -1 0

Fluorine: 0 to -1; reduced

Bromine: -1 to 0; oxidized

=0+1 -1 =0+1 -1



reduced in each of these reactions. Also

identify the oxidizing (OA) and reducing (RA)

agents.

3. SO3(g) + H2O(l) → H2SO4(aq)

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+6 -2 +1 -2 +1

Since there is no change in oxidation

number, this is not a redox reaction.

-6+6 +2

-2

-8+6

+6

+2 -2=0 =0 =0





agents.

2. 2KClO3(s) → 2KCl(s) + 3O2(g)

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+1 -2+5 +1 -1 0

Chlorine: +5 to -1; reduced

Oxygen: -2 to 0; oxidized

-6+1 +5 =0 =0+1 -1

You Try ItUse the change in oxidation number to




agents.

4. 2H2(g) + O2(g) → 2H2O(g)

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0 0 +1 -2

+2

hydrogen: 0 to +1; oxidized

oxygen: 0 to -2; reduced

-2 =0

You Try ItUse the change in oxidation number to




agents.

5. 2Al(s) + 6HCl(aq) → 2AlCl3(s) + 3H2(g)

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0 0+1 +3

+3

aluminum: 0 to +3; oxidized

hydrogen: +1 to 0; reduced

-3

-1 -1

=0+1 -1 =0

You Try It

You Try It… DO MORE

OH SNAP! Last day before the EXAM! Today’s agenda:

1. Double Replacement and Solubility Rules (you need a purple chart if you don’t have one yet)

2. Solubility Practice

3. Test Review

Announcements:

Our exam is onWEDNESDAY Feb. 17th

Please check your home access to determine what you’re missing.

The 6 weeks ends onFriday Feb. 19th

82

Soluble and Insoluble SaltsIonic compounds that

dissolve in water are soluble salts

do not dissolve in water are insoluble salts

83

Solubility Rules Soluble salts typically contain at least one ion

from Groups 1A(1), NO3−, or C2H3O2

− (acetate).

Most other combinations are insoluble.

You have this

chart (or you

should). Yours is

purple!!

How do you use this

crazy looking thing?>!

1. Look at the second

element/ion in the given

compound.

NaOH

2. Find in under “soluble or

insoluble”

NaOH

OH is insoluble, unless it’s paired

with an exception.

3. Check to see if it is paired with

an exception. If it IS with an

exception, it becomes the

opposite (soluble becomes

insoluble)

NaOH

Na is an alkali metal, which means

that it’s an exception. This means

that NaOH is SOLUBLE!!

85

Use the solubility rules to determine if each

salt is:(S) soluble or (I) insoluble.

A. Na2SO4

B. MgCO3

C. PbCl2

D. MgCl2

Learning Check

Soluble

Insoluble

Insoluble

Soluble

For the rest of the period:

you are to work on your

study guide.

This will be EXTRA CREDIT

if you complete it and

turn it in on test day.

chemical reactions and equations types of reactions

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