CHEMICAL

QUANTITIES

Measuring Matter Count Weigh Volume Each of these measurements is related

to a single quantity called the “mole”

The Mole A mole is a convenient standard

quantity used to count representative particles.

WHY?

because …. atoms and molecules are so tiny, chemists use this counting unit called the mole.

it represents 6.02 x 1023 molecules or atoms or particles

Representative particles: the type of particle that make up a substance

substance representative particles

elements atoms Molecular compounds molecules Ionic compounds formula units

Just as a dozen is always 12, a mole is always 6.02 x 1023.

This is called Avogadro’s number because Amedeo Avogadro came up with the idea!!

Who is he, you ask?.....

Amedeo Avogadro Was a lawyer and

scientist (physics) In 1811 proposed that

equal volumes of all gases contain the same number of molecules

How many? Good question!......

The number of molecules in 1 mole of gas is known to be 6.022 x 1023

He was right and so we now apply this to all molecules (not just gases).

The mole is so important to chemistry that we actually have National Mole Day. It is every October 23 from 6:02 in the morning until 6:02 in the evening.

HOW DO YOU CELEBRATE MOLE DAY?????

Better ideas……….!

Just imagine…. If you had a mole of dollars ($6.022 x

1023) and you spent $1 billion every second of every minute of every hour of every day for 70 years….

You would have spent less than 1% of your money! WOW!

Examples 1 mole of carbon = 6.022 x 1023 C atoms. 1 mole of water = 6.022 x 1023 H2O

molecules. 1 mole of sodium chloride = 6.022 x 1023

NaCl formula units. 1 mole of glucose = 6.022 x 1023 C6H12O6

molecules. Pretty simple, eh?

Converting from moles to Representative particles

multiply by 6.022 x 1023

MOLES REPRESENTATIVE

divide by 6.022 x 1023 PARTICLE

You try it….How many moles of magnesium are 3.01x

1022 atoms of Mg?

Answer: 3.01x 1022 atoms

6.02 x 1023 atoms/mol

= 0.500 x 10-1 = 5.00 x 10-2 mol Mg

Practice! Do problems #5 - 8

on page 51-52

If you want the number of atoms in a mole of a compound… you must know how many atoms are in

the compound Ex: how many atoms are in 1 mole of CO2?

1 mol X 6.022 x 1023 atoms/mol X 3 atoms

= 18.06 x 1023atoms

= 1.81 x 1024atoms

If you want the number of ions in a mole of a compound… you must know how many ions are in

the compound Ex: how many F- ions are in 1.46 mole of AlF3?

1.46 mol X 6.022 x 1023 formula units/mol X 3 F- ions

= 26.3676 x 1023 F- ions

= 2.64 1024 F- ions

Do problems #9 - 11

On page 52

Converting from representative particles reverses the process

Atoms, molecules, formula units are divided by Avogadro’s number to get the number of moles!

How many moles are present in a sample of 5.83 x 1024

molecules of CO2 ? 5.83 x 1024

molecules of CO2

6.02 x 1023 molecules /mol

= 0.984 x 101 mol of CO2

9.84 mol of CO2

Turn to page 53

Answer questions #12-15

NewStuff……

Moles

Representative Particles

Multiply by 6.02x1023

Divide by 6.02x1023

Mass

Divide by molar mass

Multiply by molar mass

Molar Mass Molar mass is the mass in grams of

one mole of any element or compound.

The units for molar mass are g/mol It can refer to atoms,molecules or

formula units. Huh?

Molar Mass Gram atomic mass……used for elements

Gram molecular mass….used for molecules

Gram formula mass.....used for ionic compounds

All of these can be referred to as

gram formula mass or molar mass …………..…what?!

Gram Atomic Mass (gam)is the mass in grams of an atom = 1gam

Numerically it is equal to its atomic mass (you know…on the periodic table!)

Ex: 1mol S = 32.1g = 1gam S 1mol Hg = 200.6g = 1gam Hg 1mol Fe = 55.8g = 1gam Fe

Example:Molar mass of carbon (aka gram

atomic mass) is the mass of one mole of carbon, which would be 12.01 g/mol

(refer to atomic mass of C on periodic table).

What would be the molar mass of He? What would be the molar mass of Ba?

Gram Molecular Mass (gmm)is the mass in grams of the atoms which

make up the molecule

Ex:

1mol SO3 = 32.0g + 3(16.0g)

= 80.1g = 1gmm

1mol C6H4Cl2 = 6(12.0g) + 4(1.0g) + 2(35.5g)

= 147.9g = 1gmm

Molar mass of water (aka gram molecular mass) would be the mass of one mole of water………. which we find by adding up the atomic masses of each element in the molecule.

Molar mass (H2O) = 2 x 1.01 = 2.02 1 x 16.0 = 16.0

18.02g/mol

What is the molar mass of sulfuric acid?H2SO4 = (2 x 1.01) + 1(32.0) + 4(16.0) =

50.01g/mol

Gram Formula Mass (gfm) is the mass in grams of the ions which

make up the ionic compound Examples: 1mol potassium iodide (KI)

39.1g + 126.9g = 166.0g = 1gfm KI 1mol ammonium carbonate (NH4)2CO3

2(14.0g) + 8(1.0g) + 12.0g + 3(16.0g)

= 96.0g = 1gfm (NH4)2CO3

All solids, liquids and gases can be converted from mass to moles and vice versa.

From mass to moles: divide by molar mass From moles to mass: multiply by molar mass

multiply by molar mass

MOLES MASS divide by molar mass

EXAMPLE: What is the mass of 4.2 mol of silver

nitrate?

ANSWER: Mass = 4.2 mol x 169.88g/mol

= 713.5g

From moles to mass…… Multiply by molar massMolar mass =

AgNO3 = (107.87) + (14.01) + 3(16.00) = 169.88 g/mol

Rasputin! Ever hear of him….?

If his murderers had calculated the correct quantity of potassium cyanide, they could have killed him with much less effort….

HCl + KCN HCN + KClhydrochloric acid potassium cyanide hydrocyanic acid potassiun chloride

However, they would have had to know about his unique medical condition first…….

HCl + KCN KCN + HClhydrochloric acid potassium cyanide potassium cyanide hydrochloric acid

KCN KCNpotassium cyanide potassium cyanide

See……..

chemistry is useful in everyday life!