ch 7: chemical reactions - chemistry€¦ · ch 7: chemical reactions on the first right side page...

CH 7: CHEMICAL REACTIONS

On the first right side page (after Ch 6 notes),

• Create a Cover page for Chapter 7. (see next slide for ideas)

• THEME: Balancing Chem Reactions, Types of Chemical

Reactions, Evidence of Chemical Reactions

• Make it the whole page

• Include COLOR!!

On the back side of cover page (left side),

• Paste the Ch 7 Learning Objectives in.

1. Research or look in your textbook any chemical reaction and write out

the balanced chemical reaction. (see example above)

2. Draw the molecular structures too for every chemical involved in the

reaction.

The above is an example of what I am looking for BUT YOU CAN’T USE IT AS YOUR COVER!!

SAMPLE COVER DESIGNS

TN Ch 7.1 Date

Title and

Highlight

Topic:

NOTES:

Write out the notes from my website.

Use different types of note-taking

methods to help you recall info (different

color pens/highlighters, bullets, etc)

When I lecture we will add more info, so

leave spaces in your notes

Summary Questions:

•2-3 sentences… What did you learn today from the notes?

•THESE ARE AT THE VERY END OF NOTES

Right Side – NOTES ONLY

Reflect

Question:

Reflect on

material by

asking a

question

(its not

suppose to

answered

notes)

TN Ch 7.1

Title and

Highlight

DRAW ANY PICTURES, FIGURES,

AND WRITE OUT ANY PRACTICE

PROBLEMS/QUESTIONS.

WE WILL ANSWER THEM TOGETHER.

LEAVE SPACES SO WE CAN ANSWER

LEFT Side – PICTURES, PRACTICE PROBLEMS, ETC

CH 7.1-7.2: CHEMICAL REACTIONS

Topic: Evidence of Chem Reaction

EQ: What evidence can you see

that a chem reaction has

occurred?

READ Ch 7.1-7.2 (pg. 205-209)

• Chemical reactions take place all around us and even inside us.

• They are involved in many of the products we use daily.

• If we could see the atoms and molecules that

compose matter, we could easily identify a

chemical reaction:

• Atoms combine with other atoms to form

compounds.

• Original molecules decompose.

• Atoms in one molecule change places with

atoms in another.

• We could know a chemical reaction has

occurred by observing these changes.

• Just remember Ch 3… a chemical change

(reaction) produced something new!!

EVIDENCE OF A CHEMICAL REACTION (VERY IMPORTANT!!!)

The following 5 provides evidence (can see

with our eyes) of a chemical reaction:

• A color change

• The formation of a solid (precipitate)

• The formation of a gas, smoke,

odor, bubbles

• The emission of light

• The emission or absorption of heat

EVIDENCE OF A CHEMICAL REACTION

NOT EVIDENCE OF A CHEMICAL

REACTION

• We can be fooled.

• When water boils, bubbles form and a gas is evolved, but no chemical reaction has occurred.

• Boiling water forms gaseous steam (still water) - no chemical change has occurred.

PRACTICE PROBLEMS #1:

• Which changes involve a chemical reaction? EXPLAIN!!

A. ice melting

B. An electric current passing through water, resulting in formation of H and O gases.

C. Iron rusting

D. Bubbles forming when a soda can is opened.

Left side

PRACTICE PROBLEMS #2:

• Which changes involve a chemical reaction? EXPLAIN!!

A. Butane burning in a lighter

B. Butane evaporating out of a lighter

C. Wood burning

D. Dry ice subliming (turns from solid to gas)

Left side

SUMMARY:

Let’s reflect…. What did you learn today from the notes? (2-3 sentences)

RIGHT side - THESE ARE AT THE VERY END OF NOTES

CH 7.3: CHEMICAL EQUATIONS

Topic: Chem Equation

EQ: What are the rules for

writing a balanced chem

equation?

READ Ch 7.3 (pg. 210-211)

CH. 7.3 NOTES -- CHEMICAL REACTIONS

•We represent chemical reactions with chemical equations.

•Chemical equations give information about the REACTANTS & PRODUCTS

Review: Reactants: ______ side of the arrow.

Products: __________ side.

Example of a Balanced Chemical Equation:

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

States of Matter (S.O.M.) - each chemical has it in parentheses next to the formula.

COMMON SYMBOLS USED IN CHEMICAL EQUATIONS

(See Table 7.1)

+ = used to separate 2 reactants or 2 products from each other

→ = “yields” or “reacts to produce”

= _____________ reaction (like a rechargeable battery)

(s) (l) (g) (aq) = phase of matter: (solid, liquid, gas, or “aqueous”)

= ___________ supplied to the reaction

MnO2 = a catalyst, (in this case, MnO2), is used to ________ ____

the reaction.

reversible

speed up

BALANCING CHEMICAL EQUATIONS

Why do you have to balance a chemical equation?

• Law of Conservation of Matter (or Mass): “Matter is neither

____________ nor _______________ in chemical reactions, ITS

CONSERVED (REARRANGED)!!!.”

• During a chemical reaction, atoms are either _________,

______________, or rearranged. The _____________ and type of

each atom stays the same.

How do you balance a chemical equation?

• __________________ are placed in front of the substances to get

the same number of atoms of each element on both sides of the

equation.

created destroyed

joined

separated number

Coefficients

DO YOU KNOW HOW TO COUNT? Practice Problem #1

How many atoms of each element are there in each compound?

a) Ca(OH)2 ___

b) C3H8O___

c) (NH4)2HPO4 ___

d) HC2H3O2 ___

Left side

RULES - Balance a chemical equation

• Use Atom inventory:

(This is how you show your work) • Split the equation in half (under the arrow) and

list the elements. • Count # atoms you see on both the reactant

AND product side. • If all atoms on each side are equal, then the

equation is called a “balanced chemical equation”

• If not (most of the time), then you must balance the equation by adding coefficients (BIG #’s in the front of chemicals.

THE CHEMICAL EQUATION: COMBUSTION OF METHANE

• We represent this skeleton (unbalanced – no coefficents) reaction with the following equation:

• With states included, the equation becomes

The left side of the equation has two oxygen atoms and the

right side has three.

Atoms cannot simply appear or disappear in chemical

equations. We must account for the atoms on both sides of the

equation.

Draw Pics also with the notes!!

To correct these problems, we must create a balanced equation.

The equation is now balanced because

the #’s of each type of atom on both sides

of the equation are equal.

(AKA…Law of Cons. of Matter is valid!!!)

Draw Pics also with the notes!!

CHECKING THE BALANCED EQUATION

• If there are no coefficients, a 1 is implied (but we never write 1’s).

• The balanced equation is as follows:

Coefficients can only be placed ___ _________ of a chemical formula.

Practice Problem #2: How many atoms of each type are indicated in the following compounds? (a) 2 (NH4)3PO4 N= ___ H= ___ P= ___ O= ___

(b) 4 KC2H3O2 K= ___ C= ___ H= ___ O= ___

(c) 3 Ca(NO3)2 Ca= ___ N= ___ O= ___

in front

Left side

RULES FOR BALANCING CHEMICAL EQUATIONS (1) You cannot change a ________________!!

Example : H2 + O2 H2O

To balance oxygen, you cannot change water’s formula to_________!

(2) You cannot place the coefficient in the ______________ of a formula!!

Example : Al + N2 AlN

To balance nitrogen, you cannot put a 2 in the middle to make _______.

(3) Reduce the coefficients to the simplest ____________ ___ ratio.

Example: 4H2 + 2O2 4H2O can be reduced to…

__H2 + __O2 __H2O

subscript

middle

whole #

Practice Problem #3: Balance Equations by adding coefficients

a) ___(NH4)2CO3 ___NH3 + ___CO2 + ___H2O

b) ___Al + ___CuSO4 ___Al2(SO4)3 + ___Cu

c) ___Fe(OH)3 ___Fe2O3 + ___H2O

d) ___Li + ___H2O ___LiOH + ___H2

Left side – leave 5 spaces between questions

SUMMARY:

CH 7.4: BALANCING EQUATIONS

Topic: Writing Chem Equations

EQ: How do you write a balanced

chem equation with no formulas?

READ Ch 7.4 (pg. 212-214)

HOW TO WRITE BALANCED CHEMICAL EQUATIONS

1.Write a skeleton (unbalanced) equation by writing correct chemical formulas. DON’T FORGET TO BALANCE THE CHARGES!! (Use Polyatomic card)

2. Once you have written all formulas, write in your S.O.M. (as many as possible).

3. Balance the equation by adding COEFFICIENTS (BIG #’s in the front).

4. VERY IMPORTANT!!...you can change only the coefficients to balance a chemical equation; never change the subscripts.

5. Rewrite final balanced equation at the end of problem (and highlight)

Practice Problem #1: Write a skeleton equation from

words:

Solid aluminum reacts with aqueous

sulfuric acid to form aqueous aluminum

sulfate and hydrogen gas

Practice Problem #2: Write a skeleton equation from

words:

Sodium reacts with bromine, when heated,

to produce solid sodium bromide.

WRITING SKELETON EQUATIONS

Practice Problem #3: Write the following equations into words using

complete sentences.

a) NaHCO3 (s) + HCl (aq) NaCl (aq) + H2O (l) + CO2 (g)

b) H2SO4 (aq) + BaCl2 (aq) HCl (aq) + BaSO4 (s)

SUMMARY:

CH 7.5: BALANCING EQUATIONS

Topic: Aqueous Solutions

EQ: How do you determine if a

solution is aqueous?

READ Ch 7.5 (pg. 214-217)

• soluble – a compound that dissolves in that liquid.

• insoluble - does not dissolve in the liquid.

• An aqueous solution is a homogeneous mixture (solution) of a substance with water.

• When ionic compounds dissolve in water, they usually dissociate (break apart) into their component ions.

The Light Bulb Demonstration

bright glow weak glow no glow

Strong Electrolyte Weak Electrolyte Nonelectrolyte

• 100% completely

dissociate into ions

•Types: Ionic

Compounds, Strong

Acids & Bases

• Examples: salt water,

. HCl, drain cleaner

• partially (not

100%) dissociate

into ions

• Types: Weak

Acids & Bases

•Examples: tap

water, vinegar

• no dissociation

• Examples: pure

(DI) water, sugar in

water, oil, alcohol

AQUEOUS SOLUTIONS: NOT ALL DISSOLVE IN WATER

• Not all ionic compounds dissolve in water.

• AgCl does not dissolve in water.

• AgCl remains as a solid, AgCl(s), within the liquid water.

• It does not dissolve or dissociate into ions.

SOLUBILITY RULES: MUY IMPORTANTE!!

SO…..

If not all ionic compounds dissolve, then how do we know without performing experiments?

We use solubility rules.

LES IS

LE. Any

compound

contains

these ions

is always

soluble

except

with the

ions listed

compound

contains

these ions

is never

soluble

except

with the

ions listed

WILL BE GIVEN TO YOU ON TESTS!! Left side!!!

SOLUBILITY: MOSTLY INSOLUBLE

Note that the solubility rules contain many exceptions.

Let’s practice how to read the

Look at carbonate (CO3 -2)

SOLUBILITY: MOSTLY INSOLUBLE

Exceptions.

For example:

• compounds containing the CO32− ion are insoluble.

• CaCO3, FeCO3, SrCO3, and CuCO3 = do not

dissolve in water. (SOLIDS)

• HOWEVER - compounds containing CO32− are

soluble when paired with Li+, Na+, K+, or NH4+.

• Li2CO3, Na2CO3, K2CO3, and (NH4)2CO3 are

soluble. = a.q.

PRACTICE PROBLEMS #1

• Practice using the solubility rules for the following compounds:

• Ca(NO3)2

• AgCl

• Ni(OH)2

Left side

Which of the following are soluble in water? a. SrSO4

b. NaNO3

c. PbCl2

d. AgBr

e. CaCl2

f. Pb(NO3)2

g. PbSO4

Left side

SUMMARY:

CH 7.6

Topic: Precipitate Rxn

EQ: How do we determine

the products of a precip. rxn?

READ Ch 7.6 (pg. 218-221)

•Precipitate reactions (rxn), reactions that form a solid (s), called a precipitate, upon mixing two aqueous solutions.

•Also called Double Replacement (DR) reactions

DR/Precipitate Rxns:

•A reaction between _____ ________________ that are (aq) that produces _____ ________________ , one of which is _____________(produces s, l, or g)

• THINK FOIL!!

General Form: ____ + ____ ____ + ____

A solid produced during a chemical reaction is called a precipitate.

two compounds

insoluble

AX(aq) BY(aq) AY(aq) BX(s)

PREDICT THE PRODUCTS OF THE FOLLOWING REACTION: (NEED

SOLUBILITY RULES!!)

Pb(NO3)2(aq) + KI (aq)

Pb(NO3)2(aq) + 2KI (aq) PbI2(s) + 2KNO3 (aq)

We know it is a solid precipitate because it is insoluble (solid) according to the solubility rules.

Precipitation

• a brilliant yellow precipitate of PbI2(s) forms.

What about….. Na Cl (aq) + KI (aq)

NaCl (aq) + KI (aq) NaI(aq) + KCl (aq) (BORING RXN!) So, if no reaction occurs….. NaCl (aq) + KI (aq) NR (no reaction)

No precipitate, liquid, or gas forms, which means no reaction.

• Precipitation reactions do not always occur when mixing two aqueous solutions.

• Sometimes…no reaction occurs.

PREDICTING PRECIPITATION REACTIONS

• The key to DR/ Precipitate reactions is only insoluble (solids) compounds form precipitates.

Rules:

1. Write a skeleton equation

2. Combine the cation (+) from one reactant with the anion (-) from the other. (THINK FOIL!!!)

Balance charges - formulas for the new products.

WRITING EQUATIONS FOR PRECIPITATION REACTIONS

3. Use the solubility rules - determine whether any of new products are insoluble = solid.

4. If all products are (aq) = soluble, there will be no precipitate. Write NO REACTION (NR) next to the arrow. (Still have to write reactants!!)

Example: Solutions of sodium carbonate Na2CO3(aq)

and copper(II) chloride CuCl2(aq) are mixed. (Balance your charges)

Na2CO3(aq) + CuCl2(aq) → CuCO3(s) + NaCl(aq)

(This is only a skeleton rxn. We still need to……)

Balance the equation.

• Only adjust coefficients, not the subscripts.

Na2CO3(aq) + CuCl2(aq) → CuCO3(s) + 2 NaCl(aq)

SUMMARY:

CH 7.8-7.9 (PART 1)

Topic: Types of Reactions

EQ: What is the difference

between the 8 types of Rxns?

READ Ch 7.8-7.9 (pg. 223-228)

GENERAL TYPES OF REACTIONS (CONTINUED)

1) _______________ Replacement:

A reaction between _____ ________________ that are dissolved in water that produces _____ ________________ , one of which is ________________ (s, l, or gas) .

General Form: ____ + ____ ____ + ____

2) A solid produced during a chemical reaction is called a precipitate.

Examples: CaCl2 (aq) + AgNO3 (aq) _________ + ________

NaOH (aq) + HCl (aq) ________ + ________

Double

two compounds

two compounds insoluble

AX(aq) BY(aq) AY(aq) BX(s)

CH 7.8 ACID–BASE REACTIONS

• 3) Acid–base reactions are reactions that form water and a salt (Ionic Compound).

Also called neutralization reactions.

SOME COMMON ACIDS AND BASES

Left side

• Write a balance equation for the following:

HNO3 + Ca(OH)2

Left side

GAS EVOLUTION REACTIONS:

4. Gas Evolution Rxns – produce a GAS!!!

1. Write a skeletal equation

HNO3(aq) + Na2CO3(aq) → H2CO3(aq) + NaNO3(aq)

(If you form this..ding ding!!)

2.You must recognize that H2CO3(aq) decomposes into H2O(l) and CO2(g) and write the corresponding equation.

HNO3(aq) + Na2CO3(aq) → H2O(l) + CO2(g) + NaNO3(aq)

3. Finally, balance the equation.

2 HNO3(aq) + Na2CO3(aq) → H2O(l) + CO2(g) + 2NaNO3(aq)

GAS EVOLUTION REACTIONS

Left side

PRACTICE PROBLEM #2

• Write a balance equation for the following:

hydrobromic acid + potassium sulfite (aq)

Left side

SUMMARY:

CH 7.8-7.9 (PART 2)

READ Ch 7.8-7.9 (pg. 223-228)

LETS REVIEW FIRST….

• Write a balance equation for CuNO3 (aq) reacting with (NH4)2S (aq) (Don’t forget S.O.M., balance charges, and coefficients)

• Write a balance equation for HNO2 (aq) reacting with KOH (aq) (Don’t forget S.O.M., balance charges, and coefficients)

CH 7.8 SEVEN TYPES OF REACTIONS

5)_______________: (sometimes called “Synthesis”)

• A reaction of _____ __________________, typically a metal and a nonmetal to form ______ ______________.

• It is the opposite of decomposition.

General Form: ___ + ___ _____

Examples: Al (s) + Cl2 (g) _______

PbO (s) + H2O (l) ______

Combination

two substances

one compound

A X AX

TYPES OF REACTIONS

6) ________________________:

• A reaction that breaks apart ______ ______________ into simpler substances, (usually two elements or an element and a smaller compound.)

General Form: _____ ___ + ___

Examples: H2O _____ + _____

KCl ___ + _____

Remember that “H,N,O,F,Cl,Br,I” elements are diatomic when alone!!

Decomposition

one compound

AX A X +

7) _________________: Reacts with oxygen gas!!!

• Combustion reactions are exothermic (they emit heat).

• A reaction between a Carbon/Hydrogen with _____ always produces the same… ________ + ________

• This reaction is too easy!! Don’t miss it!

General Form: CxHy + O2 ____ + ____

Examples: C2H2 + O2 _______ + _______

C7H6O + O2 _______ + _______

Combustion

O2 CO2 H2O

CO2 H2O

BALANCING EQUATIONS:COMBUSTION

___Al + ___O2

___ S + ___O2

Left side – Leave space to show work

PRACTICE PROBLEM #1

SUMMARY:

CH 7.8-7.9 (PART 3)

READ Ch 7.8-7.9 (pg. 223-228)

8) _____________ Replacement:

• A reaction between ____ ______________ and ___ ____________ that produces a different _____________ and ______________.

• General Forms:

____ + __ ____ + __

• The element that is trying to replace the other must be ________ _______________ than the one it is replacing.

• You must use the Activity Series to see if the reaction will happen.

• See chart _________ ___ = more reactive

Single

one compound one element

compound element

Y X AX AY

more reactive

Higher up

ACTIVITY SERIES Left side

SINGLE REPLACEMENT REACTIONS

NaCl + F2 _____ + _____

FeCl2 + K _____ + _____

HCl + Zn _____ + _____

HCl + Au _____ + _____

H2O + Na _____ + _____

H2O + Fe _____ + _____

CuNO3 + Ag _____ + _____

Left side – Leave space to show work

PRACTICE PROBLEM #1

SUMMARY:

CH 7.10

EQ: What are all 8 types of

READ Ch 7.10 (pg. 228-232)

NO BQ’s

8 TYPES OF REACTIONS:

Let’s Review

• Combination (also called synthesis)

• Decomposition

• Combustion

• Single Replacement

• Double Replacement

• Acid/Base

• Precipitate

• Gas Evolution

CH 7.7

SKIP!!

Its AP Chem topics

CH 7.7 : MOLECULAR AND COMPLETE IONIC

EQUATIONS There are rxns that occur where not ALL ions participate. • Some ions do all the work and some ions just

watch the show happen.

• To show this is an equation, we write a net-ionic equation:

• A “net ionic equation” only shows the ions that were used to make the precipitate (solid).

• Basically shows only the ions doing all the work to make the precipitate and gets rid of the useless ions.

CH 7.7 : MOLECULAR AND COMPLETE IONIC EQUATIONS

• 1st Step: Need a molecular equation (also called BALANCED equation)

• AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq)

• 2nd Step: Write an Ionic equation - shows all (aq) ionic compounds dissociated in solution. (Break them apart) Separate only (aq) into their ions. Do NOT separate any solid, liquid, or gas

compounds. They DO NOT dissociate!!

Ag+(aq) + NO3

−(aq) + Na+(aq) + Cl−(aq) → AgCl(s) + Na+(aq) + NO3–(aq)

SPECATOR IONS

• In the ionic equation, some of the ions in solution appear unchanged on both sides of the equation.

• These ions are called spectator ions because they do not participate in the reaction. (Basically they do nothing in the reaction)

WRITING CHEMICAL EQUATIONS FOR REACTIONS IN SOLUTION:

COMPLETE IONIC AND NET IONIC EQUATIONS

• 3rd Step: Cross out ALL spectator ions.

• ***To cross out, you must have same amount on each side.

• Equations such as this one, which show only the ions that actually participate in the reaction, are called net ionic equations.

Ag+(aq) + Cl− (aq) → AgCl(s)

Remember this reaction from earlier section:

Pb(NO3)2(aq) + 2KI (aq) PbI2(s) + 2KNO3 (aq)

Write the ionic and

net-ionic equations

A PICTURE OF THE REACTION:

Because K+ and NO3

- are spectator ions and are not included in the net ionic equation.

Net Ionic Equation Pb2+ (aq) + 2I-(aq) PbI2(s)

Pb2+ NO3-

K+ I- K+

PbI2(s)

DIFFERENCE BETWEEN MOLECULAR, COMPLETE IONIC, AND NET IONIC

EQUATIONS

To summarize:

A molecular (Balanced) equation is a chemical equation showing the complete, neutral formulas for every compound in a reaction.

An ionic equation is a chemical equation showing all of the species as they are actually present in solution.

A net ionic equation is an equation showing only the species that actually participate in the reaction.

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