 # It’s time to learn about... Stoichiometry: Conversions At the conclusion of our time together, you should be able to: 1. Convert a mole of a chemical.

## Presentation on theme: "It’s time to learn about... Stoichiometry: Conversions At the conclusion of our time together, you should be able to: 1. Convert a mole of a chemical."— Presentation transcript:

Stoichiometry: Conversions At the conclusion of our time together, you should be able to: 1. Convert a mole of a chemical to particles or grams of that chemical 2. Convert grams of a chemical to moles or particles 3. Convert particles of a chemical to moles or grams

Review of Molar Mass The Mass of 1 mole (in grams) Equal to the numerical value of the average atomic mass (use your periodic table, round to 2 places) 1 mole of C atoms= 12.01 g 1 mole of Mg atoms = 24.31 g 1 mole of Cu atoms = 63.55 g

Other Names Related to Molar Mass Molecular Mass: If you have a single molecule, mass is measured in amu’s instead of grams. The molecular mass is the same numerical value as 1 mole of molecules, only the units are different - grams and not amu’s. (This is the beauty of Avogadro’s Number!) Formula Mass: Same goes for ionic compounds. But again, the numerical value is the same, only the units are different.

Molar Mass of Molecules and Compounds Mass in grams of 1 mole is equal numerically to the sum of the atomic masses 1 mole of CaCl 2 = 1 mole Ca x 40.08 g/mol + 2 moles Cl x 35.45 g/mol = 110.98 g/mol CaCl 2 1 mole of N 2 O 4 = 92.02 g/mol N 2 O 4

Learning Check! A. Molar Mass of K 2 O = ? g/mol 94.20 g/mol B. Molar Mass of antacid Al(OH) 3 = ? g/mol 78.01 g/mol

Calculations with Molar Mass molar mass Grams Moles

Molar Mass as a Conversion Factor Molar Mass of the Compound 1 mole or 1 mole Molar Mass of the Compound Note that the molar mass could be that of an atom OR a molecule!

Calculations with Molar Mass molar mass Grams Moles To convert Grams to Moles: x by 1 mole Molar Mass of the Compound

Calculations with Molar Mass molar mass Grams Moles To convert Moles to Grams: x by Molar Mass of the Compound 1 mole

Example of Converting Moles to Grams Aluminum is often used for the structure of light-weight bicycle frames. How many grams of Al are in 3.00 moles of Al? 3.00 moles Al ? g Al

1. Molar mass of Al1 mole Al = 26.98 g Al 2. Conversion factors for Al 26.98 g Al or 1 mol Al 1 mol Al 26.98 g Al 3. Setup3.00 moles Al x 26.98 g Al 1 mole Al Answer = 80.94 g Al

Learning Check! The artificial sweetener aspartame (Nutra-Sweet) formula C 14 H 18 N 2 O 5 is used to sweeten diet foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame? = 0.764 mol

Avogadro’s Number as a Conversion Factor 6.02 x 10 23 particles 1 mole or 1 mole 6.02 x 10 23 particles Note that a particle could be an atom OR a molecule!

Example of Avogadro’s Number as a Conversion Factor 1. Number of atoms in 0.500 mole of Al a) 500 Al atoms b) 6.02 x 10 23 Al atoms c) 3.01 x 10 23 Al atoms 2.Number of moles of S in 1.8 x 10 24 S atoms a) 1.0 mole S atoms b) 3.0 mole S atoms c) 1.1 x 10 48 mole S atoms

Atoms/Molecules to Grams Since 6.02 X 10 23 particles = 1 mole and 1 mole = molar mass (grams) You can convert atoms/molecules to moles and then moles to grams! (Two step process) You can’t go directly from atoms to grams!!!! You MUST go thru MOLES.

Calculations molar mass Avogadro’s number Grams Moles particles Everything must go through Moles!!!

Atoms/Molecules to Grams How many atoms of Cu are present in 35.4 g of Cu? = 3.35 X 10 23 atoms Cu 35.4 g Cux 1 mol Cu 63.55 g Cu x 6.02x10 23 atoms Cu 1 mol Cu

Grams to Atoms/Molecules How many grams of Cu are present in 5.4 x 10 23 atoms of Cu? = 57 g Cu 5.4 x 10 23 atoms Cu x 1 mol Cu 6.02 x 10 23 atoms Cu x 63.55 g Cu 1 mol Cu

Stoichiometry: Conversions Let’s see if you can: 1. Convert a mole of a chemical to particles or grams of that chemical 2. Convert grams of a chemical to moles or particles 3. Convert particles of a chemical to moles or grams

Learning Check! How many atoms of O are present in 78.1 g of oxygen? 78.1 g O 2 1 mol O 2 6.02 X 10 23 molecules O 2 2 atoms O 32.0 g O 2 1 mol O 2 1 molecule O 2 2.94 x 10 24 atoms of O

Learning Check Prozac, C 17 H 18 F 3 NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. Find its molar mass. 309.36 g/mol

Learning Check! How many atoms of K are present in 78.4 g of K? = 1.21 x 10 24 atoms of K

Learning Check! What is the mass (in grams) of 1.20 X 10 24 molecules of glucose (C 6 H 12 O 6 )? = 327 g of glucose

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