 # Mole (mol): The SI base unit that measures an amount of a substance; 1 mole of molecules has a mass equal to the molecular weight in grams. Mole (mol):

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Mole (mol): The SI base unit that measures an amount of a substance; 1 mole of molecules has a mass equal to the molecular weight in grams. Mole (mol): The SI base unit that measures an amount of a substance; 1 mole of molecules has a mass equal to the molecular weight in grams. 1 mole = 6.02x10 23 atoms (molecules) 1 mole = 6.02x10 23 atoms (molecules) When looking at a chemical reaction, the number of moles are indicated by the coefficients in front of the formula’s. When looking at a chemical reaction, the number of moles are indicated by the coefficients in front of the formula’s. Avogadro’s Number: The number of molecules in one mole for any substance; Avogadro’s Number: The number of molecules in one mole for any substance; 1mole of particles = 6.02 x 10 23 2 moles of particles = 12.04 x 10 23 3 moles of particles = 18.06 x 10 23 etc...

Calculating Molecular Formula When supplied with the Empirical Formula, and the Molecular Mass, we are capable of calculating the Molecular Formula with the following equation: When supplied with the Empirical Formula, and the Molecular Mass, we are capable of calculating the Molecular Formula with the following equation: Mass MF Mass EF Example: The empirical formula is CH and the molecular mass is 26, what is the molecular formula?

Gram Formula Mass (GFM) The GFM is the total mass of any substance (element or compound) The GFM is the total mass of any substance (element or compound) Example: K 2 CO 3 (2 K atoms, 1 C atom, and 3 O atoms) Mass K = 39g Mass C = 12g Mass O = 16g (39x2) + (12x1) + (16x3) = 138 grams The gram formula mass of K 2 CO 3 = 138g

WHAT YOU KNOW!!!! GFM = 1 mole = 6.02 x 10 23 molecules = 22.4 L This is the most important information for you to memorize in order to master this unit. This is the most important information for you to memorize in order to master this unit. The above means that the GFM of any substance (element or compound) is the same thing as saying 1 mole of that substance, which is the same as saying there are 6.02 x 10 23 molecules of that substance, which is the same as saying there is 22.4 L of that same substance!! The above means that the GFM of any substance (element or compound) is the same thing as saying 1 mole of that substance, which is the same as saying there are 6.02 x 10 23 molecules of that substance, which is the same as saying there is 22.4 L of that same substance!!

Mole  Mass / Mass  Mole Converstions Table T: mole = given mass Table T: mole = given mass GFM GFM Example: If you have 54 grams of LiF, how many moles do you have? Example: If you have 2.3 moles of CuCl 2, how many grams do you have?

Stoichiometry Mole-Mole Problems: Answers how many moles of one element or compounds react with a given number of moles of another element or compound. Answers how many moles of one element or compounds react with a given number of moles of another element or compound. Example: How many moles of Ca are needed to react completely with 6 moles of H 2 O in the following reaction: Ca + 2H 2 O  Ca(OH) 2 + H 2 1. Cross out anything in the equation that the problem is not considering. 2. Write the coefficient of each substance remaining under the element or compound. 3. On top of the element or compound write the number of moles given in the problem. 4. Set up a proportion:

Percent Composition The percentage by mass of each of the elements in compound The percentage by mass of each of the elements in compound Table T: Table T: % composition = mass part x 100 mass whole mass whole Example: What is the percent by mass of magnesium in magnesium oxide (MgO)?

Percent Composition  Hydrate: a compound that incorporates water molecules into its fundamental solid structure. The compound has a dot after it followed by the number of water molecules attached.  Ex: CaSO 4 2H 2 O (SOLVE THE GFM)  The dot in the hydrate equates to an addition sign when calculating the GFM of a hydrate.

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