Moles

What is a mole? A mole is a measurement Other measurements include: Couple, dozen, ream, gross, etc.

1 mole = 6.022 x 1023 representative particles What is a mole? 1 mole = 6.022 x 1023 representative particles A HUGE NUMBER! 602,200,000,000,000,000,000,000 Avogadro's Number Memorize this number! A representative particle is the smallest unit into which a substance can be broken down without a change in composition. Atoms, molecules, formula units

How big is a mole? Assume that the height of a ream (500 sheets) of paper is 5 cm. If you stack up one mole of papers, how many round trips to the moon would the stack make? A round trip to the moon is 768,800 km.

Answer: Ream of paper (500 sheets) is approximately 5 cm, or 5 x 10-5 km That means each sheet of paper is approximately 1 x 10-7 km high If each sheet of paper is approximately 1 x 10-7 km high, then 1 mole of papers is: (1 x 10-7 km) x (6.02 x 1023)= 6.02 x 1016 km high. 6.02 x 1016 km / 768,800 km=7.83 x 1010 round trips to the moon, or 78.3 billion trips

Mole Conversions—Moles to Particles If you know the moles of a substance, you can calculate the number of particles in it Use Avogadro’s number to calculate

Mole Conversions—Moles to Particles Ex. How many water molecules are there in 2 moles of water? 2 moles H20 x 6.02 x 1023 molecules 1 mole H20 Answer: 1.20 X 1024 H2O molecules

Problems How many moles of magnesium is 1.25 x 1023 atoms of magnesium? 1.25 x 1023 atoms Mg x 1 mol Mg 6.02 X 1023 atoms Mg 2.08 X 10-1 mol of Mg

How many molecules are in 2.12 mols of propane (C3H8)? 2.12 mol C3H8 x 6.02 X 1023 molecules 1 mol C3H8 1.28 x 1024 molecules of C3H8

Think about this… If you had a mole of water, would you be able to swim in it?

How can this happen? One mole of zinc is 65.39 grams One mole of calcium is 40.08 grams One mole of magnesium is 24.31 gram

protons and neutrons each have a mass of 1 atomic mass unit (amu) one mole of atomic mass units equals 1 gram. Carbon -12 has 12 amu One mole of carbon is 12 grams

The mass of a mole of an element such as carbon this is called the gram atomic mass (gam) The mass of a mole of a covalent compound such as water this is called the gram molecular mass (gmm) The mass of a mole of an ionic compound such as NaCl this is called the gram formula mass (gfm) All three of these can simply be called the MOLAR MASS.

Finding the Molar Mass Find the molar mass of SO3 Add the atomic mass of the atoms that make the molecule. 1 S = 32 3 O: (3 x 16.0 amu)= 48 32 + 48.0 amu = 80 grams/mole

Mole Conversions—Mass to Moles 1. If you know the mass of a substance, you can calculate the number of moles EX.: You have 11.2 g of NaCl. How many moles is that?

First: Calculate the molar mass of NaCl Na = 22.99 g/mol Cl = 35.45 g/mol NaCl = 22.99 + 35.45 = 58.44 g/mol This means 1 mol of NaCl = 58.44 g NaCl

Use the molar mass to calculate the number of moles in 11.2 g of NaCl Use the “railroad track”method 11.2 g NaCl x 1 mol NaCl 58.44 g NaCl Answer: .192 moles NaCl

Mole Conversions—Moles to Mass If you know the number of moles, you can calculate the mass Ex. How many grams are in 2.50 mol of NaCl?

Use molar mass as a conversion factor. 2.50 mol NaCl x 58.44 g NaCl 1 mol NaCl Answer: 146 grams of NaCl

Practice Problems How many moles are there in 1.50 x 1023 molecules NH3? Calculate the molar mass: N2O3 ? How many moles are in 15.5 g SiO2 ? What is the mass of 14.4 mol F2 ?

Practice Problems How many moles are there in 1.50 x 1023 molecules NH3? Answer: .249 mols NH3 Calculate the molar mass: N2O3 ? Answer: 76.0 grams/mol How many moles are in 15.5 g SiO2 ? Answer: .258 mols SiO2 What is the mass of 14.4 mol F2 ? Answer: 547 g F2