MOLES!! Chemical Quantities

Counting by weighing  When things are too small to count out individually, we can “count” them by weighing them. Must know an equivalence statement first.  Conversions! If 50 grains of rice = 0.89 grams of rice, how many grains are in 857 grams?

Counting by weighing If 50 grains of rice = 0.89 grams of rice, how many grains are in 857 grams?  Solve: 857 grams x 50 grains = grains 0.89 grams

Counting by weighing  It’s important to know the mass of a certain number of items before calculating  1 paperclips = 2.3 grams  1 grain of rice = grams  1 elephant = grams  If you have 200 grams of each substance, how many objects do you have of each?

Counting by Weighing  Works for atoms too!  From Periodic Table, we know that each atom has a different mass Hydrogen 1 atom = 1.01 amu Nitrogen1 atom = amu Chlorine1 atom = amu  If I have 200 amu of each element, how many atoms of each do I have?

We count by weighing for atoms!  Amedeo Avogadro  Invented the concept of the MOLE Not the facial feature Not the furry blind animal Not the spy within a group  1 Mole = 6.02 x particles

Mole is a number!  Like a “dozen” 1 dozen = 12 objects  If you had a MOLE of dollars, how long would it take you to spend it all if you spend at $1,000,000 per second.

Mole! 1 Mole = 6.02 x particles  How many particles are in 4.9 moles?  How many moles is 6.78x10 25 particles?

Why the Mole?  If the mass number on the periodic table were in grams (instead of a.m.u.) a MOLE is the number of those atoms in that many grams!  1 mol H = 6.02x10 23 atoms H = 1.01 g H  1 mol Li = 6.02x10 23 atoms Li = 6.94 g Li  1 mol Fe = 6.02x10 23 atoms Fe = g Fe

Where did it come from?  Avogadro used pure Carbon-12 (each atom is amu) and determined the number of atoms in grams of 12 C.

Molar Mass: Moles and the Periodic Table  1 mol H = 6.02x10 23 atoms H = 1.01 g H  1 mol Li = 6.02x10 23 atoms Li = 6.94 g Li  1 mol Fe = 6.02x10 23 atoms Fe = g Fe  How many moles do I have if I have 5.0 grams of iron?  How many grams do I have if I have 0.23 moles of Lithium?

Compounds!  To determine the number of grams in 1 mole of a compound, add the molar masses of all the elements together.  H 2 O = H + H + O = 2(H) + O  H 2 O = 1.01g g g = 2(1.01)  H 2 O = g

Molar mass of compounds  Find the molar mass (grams equal to 1 mole) of the following compounds: PCl 3 Mg(NO 3 ) 2 C 12 H 22 O 11

Converting Moles to Grams  Use the conversion factor for substance X 1 mole X = (molar mass) g X  Then convert!  How many moles of phosphorus trichloride (PCl 3 ) are in 10.5 grams of PCl 3 ?  How many grams of sugar (C 12 H 22 O 11 ) are in 0.55 moles of sugar?

Gases  Kinetic Molecular Theory Matter is made of atoms/molecules Molecules are moving  The higher the temperature, the faster the molecules move, thus solid, liquid, gas As molecules collide, no energy is lost  At a certain temperature, molecules have the same energy

Gases and Moles In A Gas:  More massive molecules move slower than less massive molecules at the same energy (temperature)  Slow moving large molecules have the same pressure as fast moving small molecules (hitting side of container)  Thus, at a certain temperature and pressure, there are the SAME NUMBER OF MOLECULES WITHIN A CERTAIN VOLUME

Gases and Moles  The volume that is taken up by 1 mole of any gas = 22.4 Liters at Standard Temperature and Pressure (STP*)  *At STP Temperature is 0°Celsius Pressure is 1 atmosphere

Mole Map

2 Step Problems  The mole is a central tenet in chemistry.  In order to convert between grams, particles, or liters of gas at STP, one must first convert to moles. Determine the number of molecules in 4.5 grams of table salt (NaCl).

Volume of solids and liquids?  It is possible to convert from volumes of solids and liquids only if the density of the solid or liquid is known  ___cm 3 x ___g x ___mol cm 3 g Volume x density x molar mass = moles