Celebrate MOLE Day! October 23 rd from 6:02 a.m. till 6:02 p.m. IV. Relating Mass to Numbers of Atoms.
1. The Mole (can be abbreviated mol, but NOT m, which is the abbreviation for meter!) - the SI unit for amount of substance. A mole is the amount of a substance that contains as many particles as there are atoms in exactly 12 grams of carbon-12.
-the number of particles in exactly one mole of a pure substance. This number was determined experimentally and its value is 6.022 X 1023, which means that 12 g of carbon-12 contains 6.022 x 1023 carbon-12 atoms.
Let’s get some perspective…
If every person living on Earth (6 billion people) worked to count out one mole of oranges (or anything else), and if each person counted continually at a rate of one orange per second, it would take about 4 million years for all the oranges to be counted!
If we had a mole of sand it would cover the earth 7 times over! If you had a mole of dollar bills, you could spend a million dollars every minute of your life and never spend it all!!!
3. Molar Mass for compounds things – like atoms. Because the mole is so large, (and we now know that we cannot count out a mole of anything), how do we know when we have a mole of anything?
How to find the molar mass:
Example: find the molar mass of NaCl.
Example: find the molar mass of calcium phosphate, Ca things – like atoms. Because the mole is so large, (and we now know that we cannot count out a mole of anything), how do we know when we have a mole of anything?3(PO4)2.
1 mole = 6.022X1023 atoms OR molecules OR formula units
1 mole Al = 26.98 grams
1 atom Al = 26.98 amu
1. Gram/Mole conversions-how to convert moles to grams or grams to moles.
Example: 120 g Ca x 1 mole Ca = 2.99 mole Ca
40.1 g Ca
2. Conversions with Avogadro’s Number grams to moles.
Example: How many atoms of silver, Ag, are in 4.25 moles of Ag?
4.25 moles Ag X 6.022 x 1023 atoms Ag =
1 mole Ag
Two-step conversions: grams to moles.
Ex: How many atoms of sodium, Na, are in 5.25 g of Na?
5.25 g Na x 1 mole Na x 6.022 x 1023 atoms Na =
23 g Na 1 mole Na
Practice: What is the formula mass of barium chloride dehydrate, BaCl2 · 2H2O?
What is the formula mass of aluminum sulfate octahydrate, Al2(SO4)3 · 8H2O?