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The Mole Concept. For chemists, a mole is NOT a small furry animal. A mole is the SI unit for amount of substance. This is a dozen eggs - that's an amount. A mole is like a dozen - only MORE. One gram bar of gold. Today, gold is selling for $$$ per gram.
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The Mole Concept
For chemists, a mole is NOT a small furry animal.
A mole is the SI unit for amount of substance.
This is a dozen eggs - that's an amount.
A mole is like a dozen - only MORE.
One gram bar of gold. Today, gold is selling for $$$ per gram.
One gram bar of gold. Actual Size 9 mm X 15 mm X 2 mm 3/8 inch X 3/4 inch X 1/16 in
One gram bar of gold. 196.96655 of these bars would contain a MOLE of gold molecules.
One gram bar of gold. 196.96655 of these bars would contain a MOLE of gold molecules. How much is a mole of gold worth?
cm3 A mole is equal to 6.02 X 1023 of anything.
cm3 6.02 X 1023 is known as Avogadro's number.
Avogadro's Hypothesis: equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. He also proposed that oxygen gas and hydrogen gas were diatomic molecules.
A mole of a substance is equal to its formula mass in grams. cm3
cm3 There are 6.02 X 1023 molecules of water is this cylinder.
cm3 There are 6.02 X 1023 molecules of water is this cylinder. How do we know?
cm3 The formula mass of water is 18 amu.
cm3 Water has a density of 1 g/cm3.
cm3 18 cm3 of water has a mass of 18 grams.
cm3 18 grams of water contains a mole of molecules.
The mole concept is important because it allows us to actually WEIGH atoms and molecules in the lab. cm3
What is the mass of a water molecule? cm3
18 grams = 6.02 X 1023 H2O molecules 3 X 10-23 g / H2O molecule
2 Important Mole Calculations Convert mass to moles and moles to molecules (particles).
2 Important Mole Calculations 2. Determine the concentration of solutions - Molarity.
Most mole calculations use the Factor-Label method of problem solving- also called dimensional analysis.
First: Write what you are given.
Then: Multiply by fractions equal to one until all units cancel except what you are asked for.
Finally: Punch buttons on the calculator to get the number.
1 Setting up the problem is as important as the answer.
2 Form the habit of working neatly, canceling units as you go, and circling the answer.
3 Remember, units are just as important as numbers in the answer...
3 when the units are right, the answer will be right.
Write these conversion factors on your Paper Periodic Table RIGHT NOW: 1 mole = 6.02 X 1023 = formula mass particles atoms molecules in grams
Practice Problem #1: What is the mass in grams of 2.2 X 1015 molecules of K2S2O8? Write this problem, then put your pen DOWN until told to pick it up.
To work this problem, you would:
2.2 X 1015 molecules K2S2O8 Write what is given.
2.2 X 1015 molecules K2S2O8 Draw these lines.
2.2 X 1015 molecules K2S2O8 What does this line mean?
2.2 X 1015 molecules K2S2O8 What does this line mean?
2.2 X 1015 molecules K2S2O8 What units go here?
2.2 X 1015 molecules K2S2O8 molecules Why?
2.2 X 1015 molecules K2S2O8 molecules What units go here?
2.2 X 1015 molecules K2S2O8 grams molecules Why?
2.2 X 1015 molecules K2S2O8 grams molecules Where do we get the numbers?
Useful conversion factors: 1 mole = 6.02 X 1023 = formula mass particles atoms molecules in grams
formula mass in grams 2.2 X 1015 molecules K2S2O8 = 6.02 X 1023 molecules K2S2O8
formula mass in grams 2.2 X 1015 molecules K2S2O8 = 6.02 X 1023 molecules K2S2O8 These units cancel.
2.2 X 1015 molecules K2S2O8 270 grams = 6.02 X 1023 molecules K2S2O8 K = 2 X 39 = 78 S = 2 X 32 = 64 O = 8 X 16 = 128 270 Formula mass calculation.
2.2 X 1015 molecules K2S2O8 270 grams = 6.02 X 1023 molecules K2S2O8 K = 2 X 39 = 78 S = 2 X 32 = 64 O = 8 X 16 = 128 270 These are the units are asked for.
2.2 X 1015 molecules K2S2O8 270 grams = 6.02 X 1023 molecules K2S2O8 K = 2 X 39 = 78 S = 2 X 32 = 64 O = 8 X 16 = 128 270 The problem is worked - punch buttons to get the number.
