Unit 6: The Mole What is the MOLE?

The Mole is a unit of measurement. ► Just as 1 dozen =12 ► x atoms = 1 mole ► Also called Avogadro’s Number Number

Why do we NEED the Mole? To use the most common units of mass…. The gram. Normally, if we read the atomic mass off of the periodic table we use the units of ___________________. However, that is only for the mass of a single atom or a small group of atoms. To be able to use the unit of the _______________ we have to CONVERT using moles! 1 carbon atom = amu 1 mole of carbon = grams Atomic mass units grams

How to Calculate Molar Mass… Find the Molar Mass of water. Step One: Find the formula H 2 O Step Two: Add up the mass of all the atoms Step Three: SIG FIGS!! 2H + 1O g/mol 2(1.0079g/mol) g/mol) = g/mol

Find the Molar Mass of Ammonium Sulfate… (NH 4 ) 2 SO 4 2N +8H + S+ 4O = g/mol

Practice…  NaCl  FeCl 2  Zn(NO 3 ) 2  NaCl  FeCl 2  Zn(NO 3 ) g/mol g/mol g/mol

Calculating Percent Composition… Percent Composition is a way of determining BY MASS how much of each element is in a compound

Calculating Percent Composition Example: What is the percent of girls in this classroom? To solve this problem: Find total number of students Find total number of girls Divide number of girls by total and multiply by 100 Answer: Example: What is the percent of girls in this classroom? To solve this problem: Find total number of students Find total number of girls Divide number of girls by total and multiply by 100 Answer:

Percent Composition To Find Percent Composition of ANY molecule (using H 2 O) as example: Step One: Add up molar mass Step Two: Find the total mass of each atom in the molecule To Find Percent Composition of ANY molecule (using H 2 O) as example: Step One: Add up molar mass Step Two: Find the total mass of each atom in the molecule g/mol H : 2 x = O :

Step Three: Divide each atom by the total and multiply by 100. H: x 100 = O: x 100 = % 88.81%

Practice: What is the percent composition of Iron (III) Chloride? Molar Mass: FeCl 3 = Percent Iron: x 100 = Percent Chlorine: ( x 3) x 100 = g/mol % %

Topic 2: Conversion Factors  How do we convert between different units of measurement? Objectives: In this unit you SHOULD learn: What a conversion factor is (or be reminded of them … ) How to convert between moles and grams

Conversion Factors….  What is a conversion factor???? A conversion factor is a fraction (that always equals one) that allows you to convert between units of matter.

Converting from Moles to Grams and from grams to Moles…  Step One: Write down what you know  Step Two: Set up conversion factor  Step Three: Find molar mass (place it next to grams)  Step Four:SOLVE!

Practice:  Find the number of grams in 12.0 moles of H 2 O  Step One: 12.0 moles H 2 O

Step Two: 12.0 moles of H 2 O (_________g_) mol Step Three: Step Four: g (in sig figs = 216 g) g/mol

Find the number of moles in 2700 grams of ammonium sulfate grams (NH 4 ) 2 SO 4 (____1____mol_) g

Topic 3: More Conversion Factors Objectives: In this unit you SHOULD learn: How to use more conversion factors How to convert between moles and molecules How to convert between moles and liters How to do multi-step mole conversions

Conversions between moles and molecules How many molecules are there in 1 mole? What is another name for this number? x molecules Avogadro’s Number

Molecules and Moles… This number can be used in ________________ ______________to convert between moles and molecules. (Notice you do NOT have to find molar mass for these conversions  ) Conversion Factors

EXAMPLE 1: How many molecules are there in 3.44 moles of ammonium chloride? 3.44 moles of NH 4 Cl (_______ molecules _) mol x = 2.07 x molecules

EXAMPLE 2: How many moles are there in x molecules of dinitrogen monoxide? x molec of N 2 O (_______mol_) molecules x = moles N 2 O

Moles to Liters… We can also convert from moles to ______________. There are 22.4 Liters in 1 mole but ONLY at ________________. STP stands for ____________________________________. Standard temperature = _____________ Standard pressure = _______________ We can also convert from moles to ______________. There are 22.4 Liters in 1 mole but ONLY at ________________. STP stands for ____________________________________. Standard temperature = _____________ Standard pressure = _______________ Liters STP Standard Temperature and Pressure 273 K 1 atm

EXAMPLE 1: How many Liters in moles of carbon monoxide? moles of CO (_______ Liters _) mol mol moles of CO (_______ Liters _) mol mol = x 10 4 Liters

EXAMPLE 2: How many moles in 3.56 liters of dinitrogen tetroxide? 3.56 liters of N 2 O 4 (________mol_) Liters Liters 3.56 liters of N 2 O 4 (________mol_) Liters Liters = moles N 2 O 4

Multi-Step Conversions…  The Mole Road Map  The Mole Road Map

EXAMPLE 1: How many grams in Liters of carbon dioxide? liters of CO 2 (_____mol_) Liters liters of CO 2 (_____mol_) Liters (_______gram) mol = L of Carbon Dioxide

EXAMPLE 2: How many molecules in grams of carbon dioxide? grams of CO 2 (_____mol_) grams grams of CO 2 (_____mol_) grams 1 (___________ mlc) mol x = x molecules of Carbon Dioxide 44.01

G Topic 5: Empirical and Molecular Formulas G How can we find the identify of unknown substances? G Objectives: In this unit you SHOULD learn: G The definition of empirical and molecular formulas G How to find an empirical formula G How to find a molecular formula G Topic 5: Empirical and Molecular Formulas G How can we find the identify of unknown substances? G Objectives: In this unit you SHOULD learn: G The definition of empirical and molecular formulas G How to find an empirical formula G How to find a molecular formula

Empirical Formula… Empirical Formulas are defined as the _________________________________. Therefore, if the actual formula of a compound such as glucose is C 6 H 12 O 6 the empirical formula would be: Empirical Formulas are defined as the _________________________________. Therefore, if the actual formula of a compound such as glucose is C 6 H 12 O 6 the empirical formula would be: CH 2 O Simplified formulas

Let ’ s practice finding an empirical formula using the following data: 40.00% C, 6.72% H, 53.2% G 1.STEP ONE: Pretend the % are all grams G 2.STEP TWO: Convert all grams to moles G 1.STEP ONE: Pretend the % are all grams G 2.STEP TWO: Convert all grams to moles

1.STEP THREE: Divide all moles by the smallest number of moles G 2.STEP FOUR: Multiply (if necessary) to make all whole numbers G 3.STEP FIVE: These are now your subscripts! Write the formula. 1.STEP THREE: Divide all moles by the smallest number of moles G 2.STEP FOUR: Multiply (if necessary) to make all whole numbers G 3.STEP FIVE: These are now your subscripts! Write the formula. CH 2 O

NutraSweet is 57.14% C, 6.16% H, 9.52% N, and 27.18% O. Calculate the empirical formula of NutraSweet.

Molecular Formulas: Molecular Formulas are the actual formulas of the compound. Sometimes these are the _same_________ as the empirical formula and sometimes they are a multiple of the empirical formula. To calculate the molecular formula you must first know the _empirical formula______. Molecular Formulas are the actual formulas of the compound. Sometimes these are the _same_________ as the empirical formula and sometimes they are a multiple of the empirical formula. To calculate the molecular formula you must first know the _empirical formula______.

Practice: Find the molecular formula of NutraSweet if The molar mass of NutraSweet is g/mol STEP ONE: Find the molar mass of empirical formula STEP TWO: Divide molar mass of molecular formula by molar mass of empirical formula STEP THREE: Multiple empirical formula by number found in STEP TWO. STEP ONE: Find the molar mass of empirical formula STEP TWO: Divide molar mass of molecular formula by molar mass of empirical formula STEP THREE: Multiple empirical formula by number found in STEP TWO.

Practice II: If 4.04g of N combine with 11.46g O to produce a compound with a formula mass of amu, what is the molecular formula of this compound?