The MoleWhat's a mole?

In chemistry, a mole is a counting unit.What does that mean?

– 1 dozen = 12 units(ie eggs,donuts)– 1 mole = 6.02x1023 particles.– That's 602,000,000,000,000,000,000,000 particles!– 6.02x1023 is Avogadro's Number

A mole is used to represent lots of particles– atoms– molecules(covalent compounds)– ions– Forumula Units (ionic compounds)

The MoleIf you have 3 particles of water, what do you have?

You have 3 water molecules because H2O is molecular Covalently bonded compounds are called molecules

If you have 4 particles of table salt, what do you have? You have 4 NaCl formula units becauseNaCl is ionic Ionic compounds are called formula units

If you have 5 particles of gold, what do you have? You have 5 gold atoms because gold is an element Atoms are the unit for elements

The MoleHow do you represent 6.02x1023 in a scientific calculator?

You can type 6.02x10^23 if you want...but there's a better way!

- For graphing calculators:Type in 6.02 then the 2nd button, then the “,” button, then 23The calculator will display 6.02E23This means “6.02x1023” to the calculator.

- For other calculators there is usually a key marked “E” or “EXP” that allows you to enter numbers in scientific

notation.

How BIG is Avagadro's Number?➔6.02x1023 dollars would be enough to give every person

on Earth $87 trillion. That’s $1 million a second for the next 2.8 years.

➔A modern computer that can make up to 100 million counts per second would take almost 200 million years to count to 6.02x1023

➔If 6.02x1023 snowflakes fell evenly across the United States, the blanket of snow would cover every building in the country, including the tallest skyscrapers.

➔If you could travel at the speed of light (186,000 mi/s in a vacuum), it would take you more than 100 billion years (longer than the Universe has been around) to travel 6.02x1023 miles.

Moles & Particleso If 1 mole = 6.02 x 1023, then we can determine how many

atoms(or molecules) are in stuff.o 1 mole : 6.02 x 1023

Or 1 mol6.02 x 1023 particles

o How many silver atoms are in 3 moles of Ag?(using dimensional analysis (factor method))

3 mol Ag x 6.02 x 1023 atoms Ag =1mol Ag

Waitaminute… but why are moles on the bottom and Avogadro’s number on the top?

Since 1mol = 6.02x1023, either one can be on top, we just choose the one that will cancel out the original unit.

Mole to Particle Conversions

Examples:How many molecules of methane are in 4.50 mol of methane?

4.50 mol CH4 x 6.02x1023 molecules CH4

1 mol CH4

= 2.71x1024 molecules CH4

2.39x1024 atoms Fe x

How many moles of iron are in 2.39x1024 iron atoms?1 mol Fe = 6.02x1023 Fe atoms

1 mol Fe 6.02x1023 atoms Fe

= 3.97 mol Fe

Molar Mass• Atomic measures the mass of atoms

• Really small!• Atomic Mass is based on Carbon-12 (12C)

• Very abundant, bonds with most everything• 1 amu = 1/12 the mass of 12C• Too small to count

• Scientists decided that if 12C = 12 amu, then 12 grams of carbon = 1 mole of carbon.

• Which is equal to 6.02x1023 atoms of carbon• 1 mole of anything = its atomic mass in grams

• 1 mole of oxygen = 16.00 grams

• 1 mole of H2O = 18.02 grams• 1 mole of NaCl = 58.44 grams

• 1 atom of oxygen = 16.00 amu

• 1 molecule of H2O = 18.02 amu• 1 formula unit of NaCl = 58.44amu

Moles & Particles• Molar Mass = the mass in grams of 1 mole of any

substance.• AKA gram-formula mass• Unique for every substance• Unit: grams per mole (g/mol)

Calculations with Molar Mass• What is the mass in grams of 2 mole of iron?• molar mass of Fe = 55.85 g/mol

2 mol Fe x 55.847grams Fe = 111.60 grams Fe1 mol Fe

Mole/Mass CalculationsExamples:1. What is the mass of 0.250 moles of magnesium?

Using Periodic Table: 1 mol Mg = 24.31g Mg

2. What is the mass of 5.80 moles of carbon monoxide? Molar mass of CO = 28.01g/mol

0.250 mol Mg x24.305 g Mg

1 mol Mg= 6.08 g Mg

5.80 mol CO x28.01 g CO

1 mol CO= 162 g CO

Mole/Mass CalculationsExamples:1. How many moles would 50.45 grams of neon be equal to? 1 mol Ne = 20.18g Ne

2. How many moles would 134.0 grams of methane(CH4) be equal to? Molar mass of methane = 16.05 g/mol

50.45g Ne x1 mol Ne

20.18g Ne= 2.500 mol Ne

134.0g CH4 x1 mol CH4

16.05g CH4

= 8.349 mol CH4