The Mole Common Counting Units eggs

The Mole

Common Counting Units • eggs üdozen (12) • paper üream (500 sheets) • shoes üpair (2) • pencils ügross (144)

Counting Nails by the Pound • I want some nails for a project, but the hardware store sells nails by the pound! • How do I know how many nails I am buying when I buy a pound of nails? • Analogy üHow many atoms in a certain mass of an element?

Counting Nails by the Pound A hardware store customer buys 2. 60 pounds of nails. A dozen of the nails has a mass of 0. 150 pounds. How many nails did the customer buy? Solution map:

Counting Nails by the Pound • The customer bought 2. 60 lbs of nails and received 208 nails. He counted the nails by weighing them!

Counting Nails by the Pound • What if he bought a different size nail? üWould a dozen still weight 0. 150 lbs? üWould there be 208 nails in 2. 60 lbs? üHow would this effect the conversion factors?

Chemist’s Counting Units • need a counting unit for atoms and molecules üsince they are extremely small • mole = SI unit to measure the amount of a substance (element or compound) • 1 mole = the number of atoms in exactly 12 grams of pure carbon-12

mole • SI base unit to measure the amount of a substance (element or compound)

Counting Atoms by Moles • The number of atoms in 12 grams of Carbon-12 is 6. 022 x 1023 and we call this a mole ü 1 mole = 6. 022 x 1023 things ØLike 1 dozen = 12 things

Chemical Packages - Moles • mole = number of atoms in 12 g of C-12 ü 1 atom of C-12 weighs exactly 12 amu ü 1 mole of C-12 weighs exactly 12 g • The number of atoms in 1 mole is called Avogadro’s Number = 6. 0221421 x 1023 ü 1 mole of C atoms weighs 12. 01 g and has 6. 022 x 1023 atoms Øthe average mass of a C atom is 12. 01 amu

Avogadro (1776 -1856) Avogadro’s Number • NA = 6. 02 x 1023 of anything

Avogadro’s Number • 1 mole = 6. 0221367 x 1023 particles • rounded to 6. 02 x 1023 particles • particles can be üatoms (elements) ümolecules üformula units

How Big Is The Mole? • One mole of marbles would cover the entire Earth to a depth of fifty miles • One mole of hockey pucks would equal the mass of the moon. • One mole of rice grains is more than the number of grains of all crops grown since the beginning of time. • If one mole of pennies was divided up equally between all the people on Earth, you would have enough money to spend a million dollars every hour, 24 hours a day, for your entire life. When you died, you would have spent less than half of your pennies.

Vocabulary Word • Avogadro’s number: the number 6. 02 x 1023, tells how many pieces (atoms, molecules or formula units) in a mole

Relationship Between Moles and Mass • The mass of one mole of atoms is called the molar mass • The molar mass of an element, in grams, is equal to the element’s average atomic mass (from the Periodic Table), in amu

Mole and Mass Relationships 1 mole Sulfur 32. 06 g 1 mole Carbon 12. 01 g

Molar Mass • the mass (in grams) of a mole of substance • On your periodic tables • Round to the nearest tenth ü Hydrogen is 1. 00797 1. 0 g/mol Molar Mass is an INTENSIVE property— doesn’t depend on amount

Vocabulary Word • molar mass: mass in grams of a mole any pure substance

Moles of Compounds Too

Molecular Weight of Compounds • the molecular weight of molecules can be calculated by adding up the atomic masses Formula Mass = 1 molecule of H 2 O = 2(1. 01 amu H) + 16. 00 amu O = 18. 02 amu • since 1 mole of H 2 O contains 2 moles of H and 1 mole of O Molar Mass = 1 mole H 2 O = 2(1. 01 g H) + 16. 00 g O = 18. 02 g

Mole Relationships in Chemical Formulas • since we count atoms and molecules in mole units, we can find the number of moles of an element in a compound Moles of Compound 1 mol Na. Cl 1 mol H 2 O 1 mol Ca. CO 3 Moles of Constituents 1 mole Na, 1 mole Cl 2 mol H, 1 mole O 1 mol Ca, 1 mol C, 3 mol O 1 mol C 6 H 12 O 6 6 mol C, 12 mol H, 6 mol O

Converting from moles to particles • use conversion factors • how many roses are in 3. 5 dozen? 3. 5 dozen 12 roses = 42 roses dozen

mole conversions • how many particles are in 3. 50 moles of sucrose? 3. 50 moles 6. 02 x 1023 particles mole 21. 1 x 1023 2. 11 x 1024 particles

particle to mole conversions • how many moles are in 4. 50 x 1024 atoms of Zn? 4. 50 x 1024 atoms 1 mole 6. 02 x 1023 atoms 7. 48 moles Zn