# Unit 3: Moles!!! - Ms. Scholle

UNIT 3: MOLES!!! WHAT IS A MOLE? How BIG is a Mole??? Introduction to Project: How big is a Mole

HOW BIG IS A MOLE - EXAMPLE A mole of un-popped popcorn would cover the US to what depth? What is the area of the US? Dimensional analysis of a mole to area; compare the two FINDING THE MASS OF ONE MOLE OF AN ATOM OR MOLECULE.

To find out how much one mole weighs for an atom, you can go to the periodic table and find that elements Atomic mass ____________________________. This is also referred to as an elements _________________________.

Molar mass PRACTICE What is the mass of one mole of copper? Answer: 63.55 g What is the molar mass of lead? Answer: 207.2 g

WHAT ABOUT COMPOUNDS? Steps to finding the molar mass of a compound Step 1: List the elements in the compound and the number of atoms you have for each element. Step 2: Write the molar mass of each element and multiply it by the number of atoms. Step 3: Add the masses for each element to get the molar mass (Make sure you are following rules for sig figs)

PRACTICE Water Formula: H2O H: (2)(1.01)+ O:(1)(16.00) = 18.02 g/mol Sodium Chloride

Formula: NaCl Na: (1)(22.99)+ Cl:(1)(35.45) = 58.44 g/mol MORE PRACTICE

Sodium bicarbonate Formula: NaHCO3 Na: (1)(22.99)+ H: (1)(1.01)+

C (1)(12.01) + O: (3)(16.00) = 84.01 g/mol

Sucrose C12H22O11 C: (12)(12.01)+ H: (22)(1.01)+ O: (11)(16.00) =342.30 g/mol

WHAT ABOUT GASES? CANT JUST STICK THOSE ON A SCALE MOLE-VOLUME RELATIONSHIP Volume of a Gas Gases are difficult to weigh (mass) The volume is effected by temperature and pressure Gases must be compared at the same

temperature and pressure when finding the amount of moles of gas we have STP Standard Temperature and Pressure 00 and 1 atmosphere (atm) of pressure At STP, 1 mole of any gas occupies 22.4 L This is referred to as molar volume 1 mole = 22.4L of gas at STP

MOLAR CONVERSIONS 1. Write down your given and what you are trying to find 2. Cross out to get what you want 3. Use mole island (p.____ CRM) 4. Significant figures are determined by the given 5. Always include the substance formula and unit (REMEMBER SIG FIGS)

MOLE ISLAND EXAMPLE How many moles of boron are in 25 g of boron? 25 g of B = 2.3 mol of B

1 mol of B10.81 g of B PRACTICE How many moles of NaCl are in 100 g of NaCl? MORE CONVERSIONS We now can go between mass (grams) and moles How do we go between moles and number of

particles or vice versa? Remember that Avogadros number is the number of particles in a mole Therefore that will be our conversion factor 1 mol = 6.02 X 10 23 atoms, molecules, or representative particles CONVERTING NUMBER OF ATOMS TO MOLES

Magnesium is a light metal used in the manufacture of aircrafts, automobile wheels, tools, and garden furniture. How many moles of magnesium is 1.25 X 10 23 atoms of magnesium? KNOWNS: # of atoms = 1.25 X 1023 atoms Mg UNKNOWN: Moles of Mg = ? 1.25 X 1023 atoms Mg

1 mol Mg 6.02 X 1023 atoms Mg 2.08 X 10-1 = 0.208 mol Mg NOW YOU TRY How many moles is 2.80 x 1024 atoms of silicon?

YOUR TURN How many molecules are in 1.14 mol SO3 ? How many moles are in 4.65 X 1024 molecules of NO2 ? EXAMPLES What is the volume of 4.59 mole of CO2 gas at STP? 4.59 mol of CO2

CO2 22.4 L CO2 1 mol CO2 = 103 L of MORE PRACTICE How many moles is 5.67 L of O2 at STP?

What is the volume of 8.8 mol of CH4 gas at STP?

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