Conversions involving molar mass and Avogadros number The
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 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 in 1 mole of water? ▪ 1 mole of H 2 O= about 1/3 of a cup (18 m. L)
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 A Mole of Particles = 6. 02 x 1023 particles 1 mole C = 6. 02 x 1023 C atoms 1 mole H 2 O = 6. 02 x 1023 H 2 O molecules 1 mole Na. Cl = 6. 02 x 1023 Na. Cl formula unit
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: 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
Example 2: � 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
Practice Problems � 1. ) How many moles are in 5. 22 x 10 24 atoms of H 2 O? � 2. ) How many molecules of Na. OH are in moles of Na. OH? 23
How to calculate mass of Sodium hydroxide given moles. �How many grams are in 2. 34 moles of Sodium hydroxide? You will utilize the molar mass you calculated and use dimensional analysis. Molar mass of Na. OH 2. 34 mol Na. OH 40. 00 grams Na. OH 1 mol Na. OH = 93. 60 grams Na. OH
Calculating molecules, atoms, and formula units given mass. � How many molecules are in 42 grams of Na. OH? Avogadro’s number: (6. 02 x 1023 atoms, molecules or formula units )= 1 mole) 42 grams Na. OH 1 mole Na. OH 40. 00 grams Na. OH 6. 02 x 1023 molecules Na. OH 1 mole Na. OH Molar mass of Na. OH = 6. 32 x 10 23 molecules Na. OH
Practice Problems 1. ) Determine the molar mass for Barium Hydroxide. 2. ) How many moles are in 25. 00 g of barium hydroxide? 3. ) How many grams are in 6. 7 moles of barium hydroxide? 4. ) How many formula units are in 35. 00 g of barium hydroxide? 5. ) How many molecules are in 4. 5 moles of barium hydroxide?
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