2.C – Conserving Matter

Do Now

How many and what type of atoms are in the following examples:CH4

4NH3

6Ca(OH)2

Objectives

1. SWBAT define the law of conservation of mass.

2. SWBAT review reactants, products, coeiffients, and determining the number of atoms in a given formula.

3. SWBAT balance chemical equations with a partner.

When a car’s gas empties, where do the atoms in the gasoline go?

Keeping Track of Atoms

Law of Conservation of Matter: Matter is neither created nor destroyed.

Since chemical reactions cannot create or destroy atoms, chemical equations representing the reactions must always be BALANCED.

Atomic Perspective:

C O2 CO2

1 Carbon atom 1 oxygen molecule 1 carbon dioxide molecule

1. What are the reactants in this chemical equation?

2. What are the products in this chemical equation?

3. Are there the same number of atoms on both sides of the equation?

a. Where any atoms destroyed or created?

b. Was the Law of Conservation of Matter maintained?

2 Cu (s) + O2 (g) 2 CuO (s)

COEFFICIENTS - indicates the number of units of each substance involved.

1. Does the oxygen molecule have a coefficient?

2. What do the subscripts represent?

3. Can subscripts be removed from chemical equations?

How do we Balance Equations?

2 H2 + O2 2 H2O

Subscripts

Coefficients

# of atoms in a compound

Number of compounds in the reaction

Subscripts balance charges within a compound.

Coefficients balance atoms in an equation

What do Coefficients Really Mean?

CH4 + 2 O2 CO2 + 2 H2O

Total:1 C4 H4 O

Total:1 C4 H4 O

The equation is balanced.

H

C

H

HH

O O

O O

CO O HO

H

HO

H

H

CC

H

HH

O O

O O

CCO O HO

H

HO

H

Make an atom inventory for the following equation

Al2O3 + HCl -> AlCl3 + H2O

Is it Balanced?

SWBAT

Practice balancing equations in groups.

Taken from Kelly Deters

Make a table of elements

_____ __________

How to Balance By Inspection:

1

Reactants Products

H

O

C

CH4 + O2 H2 O CO2+_____

Taken from Kelly Deters

2 Count the number of each element or ion on the reactants and products side.

_____ __________

How to Balance By Inspection:

Reactants Products

H

O

4

2 3

2

C 1 1

CH4 + O2 H2 O CO2+_____

Don’t forget to add all the atoms of the same element together—even if it appears in more than one compound!

Taken from Kelly Deters

3Each time you add a coefficient, update your table with the new quantities of each atom.

Add coefficients to balance the numbers

_____ __________2

How to Balance By Inspection:

Reactants Products

H

O

4

2 3

2

C 1 1

2

4

44

CH4 + O2 _____ H2 O CO2+

Taken from Kelly Deters

4

Filling each coefficient location lets you and the grader know that you finished the problem rather than you left some blank because you weren’t done!

Place a “1” in any empty coefficient location

_____ __________2

How to Balance By Inspection:

Reactants Products

H

O

4

2 3

2

C 1 1

2

4

44

1 1CH4 + O2 _____ H2 O CO2+

Taken from Kelly Deters

Choosing the Order of Balancing

Save for laterElements that are uncombined

Save for laterElements that appear more than 1 time per side

StartElements that appear

only 1 time per side

StartElements in most

complicated molecules

How do you know what order to balance in?

Pb + PbO2 + H+ Pb2+ + H2O

To balance this equation, use the order: O, H, Pb

Taken from Kelly Deters

_____

How is Balancing Affected by Order?

What happens if we balance in the order determined in the last slide?

Reactants Products

H

Pb

1

2 1

2

O 2 1

4

2

_____ __________1 21 2Pb Pb+ O2 H2 O Pb2++H+_____4+

2

4

O, H, Pb

Taken from Kelly Deters

2

_____

What about a different order?

How is it different if we balance in a different order?

Reactants Products

O

Pb

2

2 1

1

H 1

2

2

_____ __________1 21 2Pb Pb+ O2 H2 O Pb2++H+_____2+

2 4

4

4

You’ll still get to the correct answer, but it will take longer and be more complicated!

H, O, Pb

Taken from Kelly Deters

Let’s Practice #1

Example:Balance the

following equation

__ HCl + __ Ca(OH)2 __ CaCl2 + __ H2O

Taken from Kelly Deters

Let’s Practice #1

Example:Balance the

following equation

__ HCl + __ Ca(OH)2 __ CaCl2 + __ H2O2 1 1 2

HOH

Did you see the “OH” polyatomic ion & change H2O to HOH?

Taken from Kelly Deters

Let’s Practice #2

Example:Balance the

following equation

__ H2 + __ O2 __ H2O

Taken from Kelly Deters

Let’s Practice #2

Example:Balance the

following equation

__ H2 + __ O2 __ H2O2 1 2

Taken from Kelly Deters

Let’s Practice #3

Example:Balance the

following equation

__ Fe + __ O2 ___ Fe2O3

Taken from Kelly Deters

Let’s Practice #3

Example:Balance the

following equation

__ Fe + __ O2 ___ Fe2O34 3 2

Homework

Pg. 181 # 6-9

Do Now

Balance the following equations:

__Cu +__AgNO3 -> __Cu(NO3)2 + __Ag

___NaClO3 --> ___NaCl + ___O2

Objectives

1. SWBAT define mole, representative particle, and molar mass.

2. SWBAT calculate the molar mass of substances.

Adopted from "Chemistry You Need to Know" by Kelly Deters

C.5 The Mole Concept

Definition:

Mole – SI unit for counting

Adopted from "Chemistry You Need to Know" by Kelly Deters

What is a counting unit?

You’re already familiar with one counting unit…a “dozen”

“Dozen” 12

A dozen doughnuts 12 doughnuts

A dozen books

A dozen cars

A dozen people

12 books

12 cars

12 people

A dozen = 12

Adopted from "Chemistry You Need to Know" by Kelly Deters

How big is a mole? Enough soft drink cans to cover the

surface of the earth to a depth of over 200 miles.

If you had Avogadro's number of unpopped popcorn kernels, and spread them across the United States of America, the country would be covered in popcorn to a depth of over 9 miles.

If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole.

Adopted from "Chemistry You Need to Know" by Kelly Deters

A Mole of ParticlesA Mole of Particles Contains 6.02 x 1023 particles

1 mole C = 6.02 x 1023 C atoms

1 mole H2O = 6.02 x 1023 H2O molecules

1 mole NaCl= 6.02 x 1023 NaCl “molecules”

(technically, ionics are compounds not molecules so they are called formula units)

6.02 x 1023 Na+ ions and 6.02 x 1023 Cl– ions

Adopted from "Chemistry You Need to Know" by Kelly Deters

What does a “mole” count in?

A mole = 6.02 1023 (called Avogadro’s number)

“mole” 6.02 1023

1 mole of doughnuts 6.02 1023 doughnuts

1 mole of atoms

1 mole of molecules

6.02 1023 atoms

6.02 1023 molecules

6.02 1023 = 602,000,000,000,000,000,000,000

This means a 12 ounce bottle of water would have 19.7 “moles” of water…a much easier-to-work-with number!

Adopted from "Chemistry You Need to Know" by Kelly

Deters

Molar Mass

Adopted from "Chemistry You Need to Know" by Kelly Deters

Definition

Molar Mass – The mass for one mole of an atom or molecule.

Other terms commonly used for the same meaning:Molecular WeightMolecular MassFormula WeightFormula Mass

Adopted from "Chemistry You Need to Know" by Kelly Deters

Mass for 1 mole of atomsThe average atomic mass = grams for 1 mole

Element Mass

1 mole of carbon atoms 12.01 g

1 mole of oxygen atoms

1 mole of hydrogen atoms

16.00 g

1.01 g

Unit for molar mass: g/mole or g/mol

Average atomic mass is found on the periodic table

Adopted from "Chemistry You Need to Know" by Kelly Deters

Molar mass for molecules

The molar mass for a molecule = the sum of the molar masses of all the atoms

Adopted from "Chemistry You Need to Know" by Kelly Deters

Calculating a Molecule’s Mass

Count the number of each type of atom

Find the molar mass of each atom on the periodic table

Multiple the # of atoms molar mass for each atom

Find the sum of all the masses

1

2

3

4

To find the molar mass of a molecule:

Adopted from "Chemistry You Need to Know" by Kelly Deters

Example: Molar Mass

Example:Find the

molar mass for

CaBr2

Adopted from "Chemistry You Need to Know" by Kelly Deters

Example: Molar Mass

Count the number of each type of atom1

Ca

Br

1

2

Example:Find the

molar mass for

CaBr2

Adopted from "Chemistry You Need to Know" by Kelly Deters

Example: Molar Mass

Find the molar mass of each atom on the periodic table2

Ca

Br

1

2

40.08 g/mole

79.91 g/mole

Example:Find the

molar mass for

CaBr2

Adopted from "Chemistry You Need to Know" by Kelly Deters

Example: Molar Mass

Multiple the # of atoms molar mass for each atom3

Ca

Br

1

2

40.08 g/mole

79.91 g/mole

Example:Find the

molar mass for

CaBr2

= 40.08 g/mole

= 159.82 g/mole

Adopted from "Chemistry You Need to Know" by Kelly Deters

Example: Molar Mass

Find the sum of all the masses4

Ca

Br

1

2

40.08 g/mole

79.91 g/mole

= 40.08 g/mole

= 159.82 g/mole+

199.90 g/mole

1 mole of CaBr2 molecules would have a mass of 199.90 g

Example:Find the

molar mass for

CaBr2

Adopted from "Chemistry You Need to Know" by Kelly Deters

Example: Molar Mass & Parenthesis

Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis.

Example:Find the

molar mass for Sr(NO3)2

Adopted from "Chemistry You Need to Know" by Kelly Deters

Example: Molar Mass & Parenthesis

Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis.

1

6

87.62 g/mole

16.00 g/mole

= 87.62 g/mole

= 96.00 g/mole+

211.64 g/mole

1 mole of Sr(NO3)2 molecules would have a mass of 211.64 g

2 14.01 g/mole = 28.02 g/mole

Sr

N

O

Example:Find the

molar mass for Sr(NO3)2

Adopted from "Chemistry You Need to Know" by Kelly Deters

Let’s Practice #2

Example:Find the

molar mass for Al(OH)3

Adopted from "Chemistry You Need to Know" by Kelly Deters

Let’s Practice #2

Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis.

1

2

26.98 g/mole

1.01 g/mole

= 26.98 g/mole

= 2.02 g/mole+

61.00 g/mole

1 mole of Al(OH)3 molecules would have a mass of 61.00 g

2 16.00 g/mole = 32.00 g/mole

Al

O

H

Example:Find the

molar mass for Al(OH)3

Adopted from "Chemistry You Need to Know" by Kelly

Deters

Using Molar Mass in Conversions

Adopted from "Chemistry You Need to Know" by Kelly Deters

Example: Moles to Grams

Example:How many grams are

in 1.25 moles of water?

Adopted from "Chemistry You Need to Know" by Kelly Deters

Example: Moles to Grams

1.25 mol H2O = _______ g H2Omol H2O

g H2O18.02

1

22.53

When converting between grams and moles, the molar mass is needed

1 mole H2O molecules = 18.02 g

HO

21

1.01 g/mole16.00 g/mole

= 2.02 g/mole= 16.00 g/mole+

18.02 g/mole

Example:How many grams are

in 1.25 moles of water?

Adopted from "Chemistry You Need to Know" by Kelly Deters

Let’s Practice #3

Example:How many moles are in 25.5 g NaCl?

Adopted from "Chemistry You Need to Know" by Kelly Deters

Let’s Practice #3

25.5 g NaCl = _______ mole NaClg NaCl

mole NaCl1

58.44

0.44

1 mole NaCl molecules = 58.44 g

NaCl

11

22.99 g/mole35.45 g/mole

= 22.99 g/mole= 35.45 g/mole+

58.44 g/mole

Example:How many moles are in 25.5 g NaCl?

Adopted from "Chemistry You Need to Know" by Kelly Deters

Example: Grams to Molecules

Example:How many molecules

are in 25.5 g NaCl?

Adopted from "Chemistry You Need to Know" by Kelly Deters

25.5 g NaCl

Example: Grams to Molecules

= _________ molecules NaCl

g NaCl

mol NaCl1

58.44

2.63 1023

1 mol = 6.021023 molecules

1 moles NaCl molecules = 58.44 g

NaCl

11

22.99 g/mole35.45 g/mole

= 22.99 g/mole= 35.45 g/mole+

58.44 g/mole

mol NaCl

molecules NaCl6.021023

1

Example:How many molecules

are in 25.5 g NaCl?

Do Now

Solve the following problem: How many moles are in 6.7 g of NaCl?

A. Given: Unknown (attain):B. What is your conversion factor?C. Solve:

Objectives

SWBAT practice conversions between moles and grams

SWBAT practice conversions between moles and molecules

Adopted from "Chemistry You Need to Know" by Kelly Deters

Let’s Practice #4

Example:How many grams is a sample of 2.75 × 1024

molecules of SrCl2?

Adopted from "Chemistry You Need to Know" by Kelly Deters

2.75 × 1024 molecules SrCl2

Let’s Practice #4

= _________ g SrCl2

molecules SrCl2

mol SrCl21

6.02 × 1023

7.24

1 mol = 6.021023 molecules

1 moles SrCl2 molecules = 158.52 g

SrCl

12

87.62 g/mole35.45 g/mole

= 87.62 g/mole= 70.90 g/mole+

158.52 g/mole

mol SrCl2

g SrCl2158.52

1

Example:How many grams is a sample of 2.75 × 1024

molecules of SrCl2?

REMEMBER:

If you are going between moles and mass use MOLAR MASS.

1 mole molar mass (g)molar mass (g) 1 mole

If you are going between moles and molecules (atoms) use AVOGADROS NUMBER.

6.02 X 1023 molecules 1 mole . 1 mole 6.02 X 1023 molecules

Do Now

Solve the following problem: How many molecules are in 0.8 moles of NaCl?

A. Given: Unknown (attain):B. What is your conversion factor?C. Solve:

Objectives

SWBAT practice conversions between moles and grams

SWBAT practice conversions between moles and molecules

Adopted from "Chemistry You Need to Know" by Kelly Deters

THINK-PAIR-SHARE

1. How many moles are in 2.3 X 1024 molecules of NaCl?

2. How many moles are in 6.8 X 1026 molecules of CO2?

3. How many molecules are in 2.3 moles of HCl?

GRAMS to MOLECULES

How many molecules are in 4.6 grams of HCl?

Do Now

Solve the following problem: How many moles are in 2.8 g of HCl?

A. Given: Unknown (attain):B. What is your conversion factor?C. Solve:

Objective

1. SWBAT review problems where molar mass converts between moles and grams.

2. SWBAT determine molar relationships amount reactants and products in a chemical equation.

Steps to Solving Equations and Molar Relationships

1. Balance the equation. 2. State the GIVEN and what you

want to ATTAIN (UNKOWN) 3. Figure out conversions. 4. SOLVE!

WORKSHEET PROBLEM #1 MOLES TO MOLES

2Mg + O2 -> 2MgO

How many moles of Mg are needed to produce 6 moles of MgO?

How many moles of O2 are needed to produce 4 moles of MgO?

How many moles of MgO will be produced when 7 moles O2 enter the reaction?

WORKSHEET PROBLEM #1 MOLES TO MOLES to Grams

2H2O2 -> 2H2O + O2

How many grams of H2O2 are needed to produce 6 moles of O2?

DO NOw

For the following equation:

2Cu + O2 -> 2CuO

1. How many moles of Cu are needed to react with 15 moles O2?

2. How many moles of CuO produced when 11 moles Cu react with sufficient O2?

Objectives

SWBAT calculate moles of product and moles of reactants.

SWAT answer questions on molar mass, g to molecules, and stoichometry.

For the following reaction:

___C5H12 + ___O2 --> ___CO2 + ___H2O

If 10 moles of C5H12 enter the reaction, how many moles of H2O are produced?

If 13 moles CO2 are produced, how many moles O2 went in?

If 10 moles of C5H12 enter the reaction, how many grams of H2O are produced?

Think-Pair-Share

Pg. 166 #1-4

Do Now

2Cu + O2 -> 2CuO

1. How many moles of Cu are needed to react with 5.6 moles O2 ?

2. How many grams of Cu will be needed to react with 5.6 moles O2 ?

Objectives

1. SWBAT calculate percent compositions.

2. SWBAT explain why knowledge of percent compositions is important to the mining process.

Percent Composition

Percent by mass of each material found in a formula unit.

Ex. In Cu2S, it is 80% copper.

Determining Percent Composition

1. Find the molar mass of the formula unit.

2. Find the percentage by dividing the part by the whole and multiplying by 100.

Example

Let’s Try this one

Find the percent oxygen in the following formulas:CO2

C6H12O6

Think-Pair-Share

How is percent composition important when mining metals?

How is it important when selecting your metal for your coin?

Homework

Read 166-168 Pg. 168 #1-4

Do Now

What percent of oxygen is found in Calcium Nitrate? Ca(NO3)2

Objectives

SWBAT answer questions to help them review for their upcoming test on chapter 2.C

SWBAT retrieve copper from it’s ore and answer questions on the lab.

C.12. Conservation in the Community

Renewable Resources: replenished by natural processesEx. Water, air, soil, plants, animals

Nonrenewable Resources: cannot be readily replenished.Ex. Natural gas, coal, oil

Conserving Resources

Green Chemistry 4 Rs

RethinkingReusingReplacingRecycling