Conversions involving molar mass and Avogadro’s number The Mole

The Mole 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)

Amadeo Avogadro 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

What can the mole be used for? 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)

So, why use the mole? It is helpful in counting a large number of items If the items are extremely small

A Mole of Particles = 6.02 x 1023 particles = 6.02 x 1023 C atoms = 6.02 x 1023 H2O molecules = 6.02 x 1023 NaCl formula unit 1 mole C 1 mole H2O 1 mole NaCl

Conversion Factors * 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

Conversions: 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

Example 1: How many atoms are in 0.500 mole of Al? Setup your problem using dimensional analysis: * Multiply across and divide by the number at the bottom 6.02 x 10 23 atoms Al 0.500 mol Al = 3.01 x 10 23 atoms Al 1 mol Al

Example 2: How many moles of Sulfur (S) are in 1.8 x 10 24 atoms of sulfur ? (Use dimensional analysis) * Multiply across and divide by the number at the bottom 1.8 x 10 24 atoms S 1 mol S = 2.99 mol S 6.02 x 10 23 atoms S

Practice Problems 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?