C HEMISTRY W ARM U P (B ACK TO CONVERSIONS!!!!) Convert the following: 5.5 dozen apples = _____ kg...

CHEMISTRY WARM UP (BACK TO CONVERSIONS!!!!)

Convert the following: 5.5 dozen apples = _____ kg apples (1 dozen

= 2.0 kg apples)

3 dozen apples = _____ bushel apples (1 dozen apples = .20 bushel apples)

SECTION 1 THE MOLE: A MEASUREMENT OF MATTER

What are three methods for measuring the amount of something?

How is avogadro’s number related to a mole of any substance?

How is the atomic mass of an element related to the molar mass of an element?

How is the mass of a mole of a compound calculated?

Mole Avogadro’s Number Representative

Particle Molar Mass

Key Concepts Vocabulary

HOW DO WE MEASURE THINGS WE CAN’T SEE LIKE THE ATOM?

The Mole – the animal The Mole – chemistry

MEASURING MATTER

Measure the amount of something by: Count (how many) Mass (g) Volume (mL or cm3)

MATTER

Composed of: Atoms Molecules Ions

Counting them would take forever!

THE MOLE-A UNIT THAT IS A SPECIFIC NUMBER OF PARTICLES

One Mole 6.02 x 1023 “representative particles” Avogadro’s Number

“Representative Particles” Atoms

1 mole of Aluminum = 6.02 x 1023 atoms Molecules

1 mole of H20 = 6.02 x 1023 molecules

Formula Units (a.k.a. ionic compounds) 1 mole of CaF2 = 6.02 x 1023 formula units

AMEDEO AVOGADRO DI QUAREGNA

Italian scientist Helped clarify the

difference between atoms and molecules

CONVERTING NUMBER OF REP. PARTICLES TO MOLES

Generic conversion:1 mole = 6.02 x 1023 “representative particles”

Examples: How many atoms in one mole of Copper?

How many formula units in 2 moles of NaCl?

PRACTICE

How many atoms are on three moles of Calcium?

How many molecules are in 2.5 moles of Al2Cl6?

How many formula units are in 10 moles of NaCl?

PRACTICE WORKSHEET

WARM UP

How many moles is 2.80 x 1024 atoms of Silicon?

How many formula units in 2 moles of MgBr2?

CONVERTING MOLES TO NUMBER OF ATOMS (IN A COMPOUND)

First, figure out the number of atoms in the compound.

Example: H20 3 atoms per molecule

1 mole of H20 contains 6.02x1023 molecules BUT each molecule of water contains 3 atoms

Moles Molecules Atoms

CLASS EXAMPLE:

Propane is a gas used for cooking and heating. How many atoms are in 2.12 mol of propane? (C3H8)

PRACTICE:

How many atoms are in 1.14 mol of SO3?

How many moles are in 4.65x1024 atoms NO2?

THE MASS OF A MOLE OF AN ELEMENT

MOLAR MASS

Numbers under the elements on the periodic table

The mass of ONE mole of a substance Example:

Molar mass of Carbon = 12.0 grams 1 mole of Carbon = 12.0 grams

Molar Mass of Oxygen = 16.0 grams 1 mole of Oxygen = 16.0 grams

EXAMPLE

How many moles is 2 grams of Lithium?

How many grams is 5 moles of Tin?

ONE MOLE OF VARIOUS ELEMENTS

MOLAR MASS CONTINUED…JUST THINK!

1 mole of hydrogen has 6.02x1023 atoms and weighs 1.008 grams…

1 mole of carbon has 6.02x1023 atoms and weighs 12 grams…

How can they have the same number of atoms but weigh different amounts?

THE MASS OF A MOLE OF A COMPOUND

MOLAR MASS OF A COMPOUND

To calculate the molar mass of a compound: Separate out EACH element Count the number of that element Multiply by the molar mass Add the masses of the elements in the

compound

Example: SO3Element Number

ofMolar Mass

Total Mass

S

O

EXAMPLE

H2O

CH4

C6H12O6

SECTION 1 ASSESSMENT - JIGSAW 1. What are three ways to measure the amount

of something? 2. Describe the relationship between Avogadro’s

number and one mole of any substance. 3. How is the atomic mass of an element related

to the molar mass of the element? 4. How can you calculate the mass of a mole of

a compound? 5. How many moles is 1.50 x 1023 molecules of

NH3? 6. How many atoms are in 1.75 mol CHCl3?

7. What is the molar mass of CaSO4? 8. How many moles are in 4.65 x 1024 molecules

of NO2?

SECTION 2

Convert the mass of a substance to the number of moles

What is the volume of a gas at STP

Avogadro’s hypothesis

Standard Temperature and Pressure (STP)

Molar Volume

Key Concepts Vocabulary

THE MOLE-MASS RELATIONSHIP

Use the molar mass of an element or compound to convert between the mass of a substance and the mass of a substance.

Conversion factor: molar mass = 1 mole

Equations: Mass(grams) = number of moles x

mass(grams) 1

mole

Moles = number of grams x ___1 mole____ mass(grams)

Molar Mass

CLASS EXAMPLES:

Aluminum satellite dishes are resistant to corrosion because the aluminum reacts with oxygen in the air to form a coating of aluminum oxide (Al2O3). This tough, resistant coating prevents any further corrosion. What is the mass of 9.45 mol of aluminum oxide?

CLASS EXAMPLE

When iron is exposed to air, it corrodes to form red-brown rust. Rust is iron(iii)oxide (Fe2O3). How many moles of iron oxide are contained in 92.2 g of pure iron oxide?

PRACTICE

Find the mass in grams of 4.52 x 10-3 mole C20H42.

Calculate the mass, in grams, of 2.50 mole of iron(ii)hydroxide.

PRACTICE

Find the number of moles in 3.70 x 10-1 g of boron.

Calculate the number of moles in 75.0 g of dinitrogen trioxide.

PRACTICE WORKSHEET

PRACTICE: FIND THE MASS, IN GRAMS, OF 1.00 X 1023 MOLECULES OF N2.

PRACTICE: FIND THE MASS IN GRAMS OF 2.00 X 1023 MOLECULES OF F2

PRACTICE: HOW MANY ATOMS OF NITROGEN ARE IN 1.2 GRAMS OF ASPARTAME? C14H18N2O5

PRACTICE: FIND THE MASS IN 2.6 X 1043 MOLECULES OF LITHIUM BROMIDE.

THE MOLE-VOLUME RELATIONSHIP

AVOGADRO’S HYPOTHESIS

The equal volumes of gases at the same temperature and pressure contain equal numbers of particles Despite differences in the size of the atoms Due to the fact that the gas particles are so far

apart

S.T.P.

Gases are measured at Standard Temperature and Pressure B/C of variations that result in volume

STP Temperature: 0 degrees Celcius (273 K) Pressure: 101.3 kPa or 1 atm

MOLAR VOLUME

At STP: 1 mol or 6.02 x 1023 representative particles

of any gas occupies a volume of 22.4 L.

CALCULATING VOLUME AT STP

Convert MOLES of gas to the VOLUME of gas at STP

Conversion factor: 22.4 L = 1 mol

CLASS EXAMPLE:

Sulfur dioxide is a gas produced by burning coal. It is an air pollutant and one of the causes of acid rain. Determine the volume, in liters, of 0.60 mol sulfur dioxide at STP.

EXAMPLES

What is the volume of these gases at STP? 3.20 x 10-3 mol CO2

3.70 mol N2

EXAMPLES

At STP, how many moles does each of the following gases occupy?

1.25 L He

0.335 L C2H6

PRACTICE

What is the volume, in Liters, of 15 g of H2 at STP?

What is the volume, in Liters, of 3.4 x 1028 molecules of O2 at STP?

PRACTICE WORKSHEET

CALCULATING MOLAR MASS FROM DENSITY

Density: Measured in grams per liter (g/L)

General Equation Molar Mass = density at STP x molar volume

at STP

Grams = grams x 22.4L Mole L Mole

CLASS EXAMPLE

The density of a gaseous compound containing carbon and oxygen is found to be 1.964 g/L at STP. What is the molar mass of the compound?

EXAMPLES

A gaseous compound composed of sulfur and oxygen, which is linked to the formation of acid rain, has a density of 3.58 g/L at STP. What is the molar mass of this gas?

EXAMPLES

What is the density of krypton at STP?

SECTION ASSESSMENT (10.2)