Do Now – April 4(5), 2009

1. What is one thing you did over Spring Break that was different than your normal routine?

2. List three things - any things - that you know about CHEMISTRY!

Agenda

• Do Now/Announcements• Review Unit 4• Welcome to Unit 5!• Moles!• Molar Mass• Molecular Weight• Exit Ticket

ReviewMake your own Quiz-Quiz-Trade

cards• Each person will make one card within the topic

assigned to your group• Use your notes to help you make your question

cardsGroup 1: Parts/Definition Chemical FormulasGroup 2: Examples of compounds/formulasGroup 3: Characteristics of ionic compoundsGroup 4: Characteristics of covalent compoundsGroup 5: How to name ionic/covalent compoundsGroup 6: Chemical reactions/evidence of reactions

Objectives

• SWBAT describe the mole as a counting unit for tiny particles.

• SWBAT determine the molar mass of elements.

• SWBAT calculate the molecular weight of compounds.

Happy Mole Day!

(After the fact)The mole is so important that it has an

entire day dedicated to it.Mole Day is a national celebration observed from 6:02 a.m. to 6:02 p.m. on October 23rd (10/23) every year

The Mole Pledge…

I pledge allegiance to the mole, to the

International Union of Pure and Applied

Chemistry, and to the atomic mass for which it stands, one number,

most divisible, with atoms and molecules

for all.

More About the Mole

We use the mole to count particles

Remember that atoms are VERY, VERY small!

Since we can’t count individual particles, we use the mole as a

counting unit

More About the Mole

The mole is a unit used to measure the amount of a

substance

Add to Vocabulary Log!

More About the MoleThe mole as a unit of measurement is based

on the work done almost 200 years ago by Amadeo AvogadroHis work led to the

association of the number

6.02 x 1023 with the

mole

Avogadro’s Number

6.02 x 1023 is calledAvogadro’s Number

6.02 x 1023 is written inscientific notation

6.02 x 1023 is equal to…602,000,000,000,000,000,000,000

Avogadro’s Number

Avogadro’s Number (aka the mole) is similar to a dozen

1 dozen roses = __?__ roses1 dozen eggs = __?__ eggs

1 dozen donuts = __?__ donuts

12

12

12

Avogadro’s Number

Avogadro’s Number = 6.02 x 1023

1 mole eggs = ____?____ eggs1 mole roses = ____?____ roses

1 mole donuts = ____?____ donuts1 mole particles = ____?____

particles

6.02 x 1023

6.02 x 1023

6.02 x 10236.02 x 1023

How Chemists Use the Mole

• In lab, chemists will measure out moles of substances

• Then, they convert the number of moles to number of grams

Hey, can I get 3.0 moles of sodium hydroxide please?

Molar MassMolar Mass

Molar mass is the mass in grams of one mole of any

pure substanceAdd to Vocabulary Log!

The molar mass is of any element is numerically equal to its atomic

mass and has the units…

grams/mole = g/molWrite down units!

Molar Mass

•In other words…molar mass (molecular weight) is how “heavy” the substance is

•Units: g/mol = “grams per mole”

Molar Mass• Remember, the molar mass

of any element is numerically equal to its atomic mass (get this off the periodic table!) with the unit g/mol

• Examples:1. Manganese = 55.0 g/mol2. Scandium = 45.0 g/mol3. Boron = 10.8 g/mol

Molar Mass Practice - Your turn!

• Determine the molar mass of each of the following elements:

1. Tantalum =2. Phosphorus =3. Zinc = 4. Lithium =

181.0 g/mol31.0 g/mol

65.4 g/mol6.9 g/mol

Molecular Weight

•Molecular weight is the total mass of a compound (or molecule)

Add to Vocabulary Log!

Steps to Calculate Molecular Weight

1. Count the number of moles (atoms) of each element.

2. Use periodic table to find molar mass of each element

3. Calculate each element’s contribution to the molecular weight.

4. Add up each element’s contribution.

Molecular Weight Example 1

Calculate the molecular weight ofsodium fluoride - NaF

Step 1: 1 mol Na, 1 mol FStep 2: molar mass of…

Na = 23.0 g/molF = 19.00 g/mol

Step 3: each element’s contribution to MW1 x 23.0 g/mol = 24.31 g/mol1 x 19.00 g/mol = 19.00 g/mol

Step 4: 23.0 g/mol + 19.00 g/mol = 42.0 g/mol

Molecular Weight Example 2

Calculate the molecular weight ofmagnesium chloride - MgCl2

Step 1: 1 mol Mg, 2 mol ClStep 2: molar mass of…

Mg = 24.3 g/molCl = 35.5 g/mol

Step 3: each element’s contribution to MW1 x 24.3 g/mol = 24.3 g/mol2 x 35.5 g/mol = 71.0 g/mol

Step 4: 24.3 g/mol + 71.0 g/mol = 95.3 g/mol

Molecular Weight Example 3

Calculate the molecular weight ofbarium nitrate - Ba(NO3)2

Step 1: 1 mol Ba, 2 mol N, 6 mol OStep 2: molar mass of…

Ba = 137.33 g/molN = 14.01 g/molO = 16.00 g/mol

Step 3: each element’s contribution to MW1 x 137.33 g/mol = 137.33 g/mol2 x 14.01 g/mol = 28.02 g/mol6 x 16.00 g/mol = 96.00 g/mol

Step 4: 137.33 g/mol + 28.02 g/mol + 96.00 g/mol = 261.35 g/mol

Molecular Weight PracticeYour turn!

• Name the following compounds and calculate the molecular weight of each:

1. H2O2. NaCl3. CO2

4. O3

5. Ca3(PO4)2

18.0 g/mol59.8 g/mol

44.0 g/mol48.0 g/mol

310.0 g/mol

Wrap-Up of Today’s Learnin!

• Review• What is Mole Day?• What is the mole used for?• What is Avogadro’s number?• What is molar mass? • How do you determine the molar

mass of an element?• What is molecular weight?• How do you calculate the molecular

weight of a compounds?

Exit Ticket

1. What is a mole used for in chemistry?

2. What is the molar mass of oxygen?3. Calculate the molecular weight of

barium hydroxide, Ba(OH)2.