Conversions involving molar mass and Avogadro’s number

A unit of measurement for counting atoms or molecules

1 Mole = 602 billion trillion
 602,000,000,000,000,000,000,000
 6.02 X 1023 (this is known as Avogadro’s number)

Avogradro’s number is named in honor of
Amedeo Avogadro (1776 – 1856)
 He studied quantities of gases and discovered that
no matter what the gas was, there were the same
number of molecules present

We can count anything using the mole
 Example:
▪ 1 mole of M & M’s would stretch from here to the sun
and back 200 billion times
▪ * assuming m&m’s are 1 cm in diameter and the distance to the sun is 93 million miles
▪ Can you swim in1 mole of water?
▪ 1 mole of H2O= about 1/3 of a cup (18 mL)

It is helpful in counting a large number of
items

If the items are extremely small
1 mole C
= 6.02 x 1023 C atoms
1 mole H2O = 6.02 x 1023 H2O molecules
23
1 mole NaCl = 6.02 x 10 NaCl formula unit
* 1 mole = 6.02 x 1023 particles
Note: Particles could refer to atoms, molecules, formula
units
* 1 mole = molar mass (g) of compound being used

MUST use dimensional analysis

MUST use the molar mass if grams are used
in the problem

Be able to convert from
 Moles to atoms or molecules
 Moles to grams
 Grams to moles

How many atoms are in 0.500 mole of Al?
 Setup your problem using dimensional analysis:
23 atoms Al
6.02
x
10
0.500 mol Al
1 mol Al
= 3.01 x 10 23
atoms Al
 * Multiply across and divide by the number at the bottom

How many moles of Sulfur (S) are in 1.8 x 10 24
atoms of sulfur ?
 (Use dimensional analysis)
1.8 x 10 24 atoms S 1 mol S
= 2.99 mol S
6.02 x 10 23 atoms S
 * Multiply across and divide by the number at the bottom

1.) How many moles are in 5.22 x 10 24 atoms
of H2O?

2.) How many molecules of NaOH are in 23
moles of NaOH?