Warm-Up Calculate Molar Mass K2O PCl5 LiF

The Mole... J. McLeod

Objectives Describe methods of measuring the amount of something. Define Avogadro’s number as it relates to a mole of a substance. Distinguish between the atomic mass of an element and its molar mass. Describe how the mass of a mole of a compound is calculated. Describe how to convert the mass of a substance to the number of moles of a substance, and moles to mass. Describe how to convert the volume of a substance to the number of moles of a substance, and moles to volume.

What is a mole?

The mole… Abbreviated (mol) It is an amount, such as… Pair: 1 pair of shoelaces = 2 shoelaces Dozen: 1 dozen oranges = 12 oranges Gross: 1 gross of pencils = 144 pencils Ream: 1 ream of paper = 500 sheets of paper

1 mole = 6.02 x 1023 Definition That’s 602,000,000,000,000,000,000,000 We call this number Avogadro’s number after Amadeo Avogadro (1766-1856)

Definition Field Trip!!!!

Definition = 1 mol C = 6.02 x 1023 atoms C = 12 grams C

Atomic Mass is the average of all isotopes of a given element. Review Atomic Mass is the average of all isotopes of a given element. 1 amu = 1/12 of a C-12 atom.

Molar Mass Atomic Mass = Molar Mass for an element Molar mass is the mass of 1 mole of a compound. It is calculated by adding each of the atomic masses of the elements making up the compound. Units for molar mass are g/mol.

Diatomics Diatomics…. You need a highlighter!!

Calculating Molar Mass Example #1: What is the molar mass of carbon (C)? C: 1 x 12.00 = 12.00 g/mol 1 mole of carbon = 12 grams of carbon Example #2: What is the molar mass of oxygen (O2)? O: 2 x 15.99 = 31.98 g/mol 1 mole of oxygen = 31.98 grams of oxygen.

Calculating Molar Mass Example #3: What is the molar mass of Water (H2O)? H: 2 x 1.008 = 2.016 g/mol O: 1 x 15.99 = 15.99 g/mol H2O = 18.006 g/mol 1 mole of water = 18.006 grams of water

Calculating Molar Mass Example #4: What is the molar mass of sodium chloride (NaCl)? Na: 1 x 22.99 = 22.99 g/mol Cl: 1 x 35.45 = 35.45 g/mol NaCl = 58.44 g/mol 1 mole of NaCl = 58.44 grams of NaCl

1 mole of Li2Cr2O7 = ___________ g of Li2Cr2O7 Your Turn Calculate the molar mass for lithium dichromate: Li2Cr2O7 1 mole of Li2Cr2O7 = ___________ g of Li2Cr2O7

Molecules, atoms, or ions Conversion Road Map Using the flowchart we can convert between moles, mass, molecules, or liters: Molecules, atoms, or ions Moles Grams Liters 6.02x1023 22.4 Molar mass

Rules For Conversion Write Units Map Set Up Problem Write Given Use a T box for each step of the map Make sure your units cancel! Write your answer with correct units

Use Of Molar Mass How many grams of nitrogen are in 1.25 moles of nitrogen (_______)? Units Map: mol (N2)  grams (N2) 1.25 mol N2 What’s the formula for Nitrogen? 28 grams N2 = 35.0 g N2 1 mol N2

Use of Avogadro’s Number How many atoms of iron are in 2.76 moles of the metal? Map: mol Fe  atoms Fe 2.76 moles Fe 6.022 x 1023 atoms Fe = 1.61 x 1024 atoms Fe 1 moles Fe

Use of Volume How many moles of carbon monoxide are in 26.7L of carbon monoxide? Units Map L CO  mol CO 26.7 L CO 1 mol CO = 1.19 mol CO 22.4 L CO

Use of Molar Mass & Avogadro’s # How many molecules of Iodine are in 25g of Iodine (____)? Units g I2  mol I2  molecules I2 25 g I2 I2 1 mol I2 6.022x1023 molecules I2 253.81 g I2 1 mol I2 =5.93x1022 molecules I2

Ticket Out The Door In your groups, compare and contrast the process to convert moles to grams and that to convert moles to atoms or particles. WHAT’S SIMILAR? WHAT’S DIFFERENT?