Mole Conversions

Chemistry is really really really small stuff Because chemical reactions often involve large numbers of small particles, chemists use a counting unit called the mole to measure the amount of a substance. Mole (mol) 6.022 x1023 particles of substance. A dozen = _______

The mol One mole of shoes would be ___________________ shoes One mole of elephants would be _________________ elephants These would not weigh the same.

Avogadro vs. brown 1827

Molar mass Is the MASS of one MOLE of an element. This is the weight on the periodic table. Unit: g/mol A mole of carbon is ______________ carbon atoms. A mole of carbon weighs ______________ grams per mole. A mole of nitrogen is ______________ nitrogen atoms. A mole of nitrogen weighs ____________ grams per mole.

Molar mass of a compound Add up the weights of all the atoms involved, A mole of carbon dioxide is ____________ CO2 molecules. A mole of carbon dioxide weighs ________________ g/mol.

Let’s practice Find the molar mass for each of the following atoms or molecules: 1. one mole of arsenic.______________ 2. one mole of rubidium ______________ 3. One mole of NO3 ______________ 4. One mole of NH3 _____________

Mole-mass conversions One mole of CO2 weighs ____________ grams. How much would two moles of CO2 weigh? _____________ How many moles would you have if you only had 22.01 grams of CO2? These are molemass and massmole conversions

Mole-mass conversions If you have 55.0 grams of CO2, how many moles of CO2 do you have? Your conversion factor of grams to moles OR moles to grams is the MOLAR MASS (or weight from the periodic table). Conversion Factor is: Now we try it:

Mass-mole conversions To go from moles to grams, do the same as before, but flip your conversion factor. If I have 144 grams of H2O, how many moles of H2O do I have? Conversion Factor: Now we try it:

Chemical equations are like recipes They tell you how many of each item you need. Example: Example --1 cup flour --2 Hydrogens --1/2 cup sugar --2 Oxygens --2 tbsp butter Makes One H2O2 --2 tbsp water Makes One Pie Crust

Mole ratios Instead of using “cups” and “tablespoons” in our “recipes” (chemical equations) we use “moles.” The balanced chemical equation tells us how many moles of each element are present. H2 + O2  H2O2 This is read as:

Converting with mole ratios If the recipe that makes one pie crust needs 1 cup of flour, how many cups of flour are needed for two pie crusts? That’s mole ratios! To convert moles of one reactant or product to another reactant or product, use your recipe guidelines (moles).

Converting with mole ratios How many moles of O2 are needed if I have 8.00 moles of H2O according to the following reaction? ___H2 + ___O2  ____H2O First, what is the conversion factor/mole ratio? Now complete the problem: