More about reactions!!! Coefficients…..again 2Cu (s) + O 2 (g)  2CuO (s) Would the coefficients be of much use in the lab?????

There are units on the coefficients called the ‘mole’ 2Cu (s) + O 2 (g)  2CuO (s) Chemists say: 2 moles of Cu react with 1 mole of O 2 to produce 2 moles of CuO

So…. When chemists talk about a “mole,” what exactly are they talking about??? Cute… but no… Not quite… Ummm… I don’t think so x THAT’S IT!

That’s right, in chemistry, a “mole” is a number! Just like a “dozen” is 12 and a “gross” is 144, a “mole” is simply a word that stands for a number: 6.02 x It is also called Avogadro’s number named for the chemist who discovered it

So… What is so special about the number 6.02 x ? For one thing, it represents a very, very, VERY large quantity. If written out, it would be: 602,000,000,000,000,000,000,000. That’s 602 million, million, billion! That’s big!

How big you ask… Consider the following examples. (And come up with your own if you want. They’re really not that hard to do…)

This computer has a remarkably fast processor: 1.83 GHz. That means, for example, that it is capable of counting to 1,830,000,000 every second! So… at that rate, how long do you think it would take this computer to count to 1 mole???

At 1,830,000,000 per second, it would take this computer a little over ten million years to count to 1 mole!! (That’s a lot of counting!) By the way, factor label makes this calculation fairly simple: 6.02 x counts 1sec 1.83x10 9 counts X 1min 60 sec X 1 year 365 day X 1 day 24 hr X 1hr 60 min X = 1.04 x 10 7 years = 10.4 million years

A grain of rice is pretty small. It takes about fifty grains of rice to fill a tiny one-milliliter box! Even still, one mole of rice grains would be HUGE… Take a guess: How much space would be taken up by one mole of rice grains?

One mole of rice – that’s 6.02 x grains – would cover the entire planet Earth… And… in case you were wondering how this was calculated: 6.02 x grains Earth’s radius = 6400 km = 6.4 x 10 6 m Surface area of a sphere = 4  r 2 Surface area of Earth = 4  (6.4 x 10 6 m) 2 = 5.1 x m 2 = 1.2 x m 3 Height = Volume Area = 23.5 m 1 mL 50 grains X 1 m 3 1 x 10 6 mL X 1.2 x m x m 2 = over 23 meters deep! Volume of all that riceArea that rice has to cover

That’s so important, it’s worth repeating: The mole provides a simple way for us to “count out” atoms and molecules by weighing them.

But why is a mole such a big number????? Because atoms are so small……..remember no one has ever seen an atom.

To understand how this works, let’s take a look at the periodic table: Take Cu for example We can see that the average mass for a Cu atom is Cu Cu

So how much would a mole of Cu weigh? 29 Cu The mass of one mole of Cu is simply Cu’s atomic mass expressed in grams. 1 mole Cu = g = 6.02 x atoms Cu

And does this neat little trick work for every element in the table? Let’s try neon. We can see that the average mass for a neon atom is Ne Ne

So how much would a mole of Ne weigh? It tells us that one mole of Ne weighs grams. How convenient is that! 10 Ne

So now, take out a periodic table and try answering the following questions. As you figure out the answers, record them on the Mole Powerpoint and Video Notesheet available on Kdocs. Copy it to your notebook!

1. How much would one mole of He weigh? Click on the right answer. 1 g2 g4.003 g6.02x10 23 g

1. How much would one mole of He weigh? 1 g2 g4.003 g6.02x10 23 g Sorry, try again

1. How much would one mole of He weigh? 1 g2 g4.003 g6.02x10 23 g Sorry, try again

1. How much would one mole of He weigh? 1 g2 g4.003 g6.02x10 23 g CORRECT! One mole of He would weigh g Write that answer on your worksheet, and then try the next question.

2. How much would one mole of Ca weigh? g1 g12 g6.02x10 23 g

2. How much would one mole of Ca weigh? 1 g12 g40.08 g6.02x10 23 g Sorry, try again

2. How much would one mole of Ca weigh? 1 g12 g40.08 g6.02x10 23 g Sorry, try again

2. How much would one mole of Ca weigh? 1 g12 g40.08 g6.02x10 23 g CORRECT! One mole of Ca would weigh g. Write that answer on your worksheet, and then try the next question.

3. How many atoms would be present in one mole of He? 1 atom2 atoms atoms6.02x10 23 atoms

3. How many atoms would be present in one mole of He? 1 atom2 atoms atoms6.02x10 23 atoms Sorry, try again

3. How many atoms would be present in one mole of He? 1 atom2 atoms atoms6.02x10 23 atoms Sorry, try again

3. How many atoms would be present in one mole of He weigh? 1 atom2 atoms atoms6.02x10 23 atoms CORRECT! In one mole of He there would be 6.02x10 23 atoms present. Write that answer on your worksheet, and then try the next question.

4. How many atoms would be present in one mole of Ca? 1 atom2 atoms atoms6.02x10 23 atoms

4. How many atoms would be present in one mole of Ca? 1 atom2 atoms atoms6.02x10 23 atoms Sorry, try again

4. How many atoms would be present in one mole of Ca? 1 atom2 atoms atoms6.02x10 23 atoms Sorry, try again

4. How many atoms would be present in one mole of Ca? 1 atom2 atoms atoms6.02x10 23 atoms CORRECT! In one mole of Ca there would be 6.02x10 23 atoms present. Write that answer on your worksheet, and now let’s return to the tutorial.

So what have we learned so far? 1) One mole of any element weighs its atomic mass in grams as shown on the Periodic Table. (thus one mole of C weighs g) 2) One mole of any element contains 6.02 x atoms. (thus one mole of C contains 6.02 x atoms)

But what about compounds like water (H 2 O), carbon dioxide (CO 2 ) and propane (C 3 H 8 )… Does the mole apply to them too? ABSOLUTELY! But there is a difference… When we talk about 1 mole of an element like C, we are talking about 6.02x10 23 atoms of C… That’s 6.02x10 23 of these: But when we talk about 1 mole of a compound like H 2 O, for example, we are talking about 6.02x10 23 molecules of H 2 O… That’s 6.02x10 23 of these: O H H CCCCCCCCCCCCCCCCCCCCCCCCCCC O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H O H H CC

How much would one mole of water H 2 O weigh? HINT: use the Periodic Table. If you were thinking g, then good job! 2( grams) + 1( grams) = grams How much would one mole of CF 4 weigh? That’s one C and four F’s: 1( grams) + 4( grams) = grams And one mole of CF 4 would weigh g

Again, using a periodic table (and perhaps a calculator if you need one), try answering the following questions? As you figure out the answers, record them on the mole tutorial work sheet.

5. How much would one mole of CO 2 weigh? 40.0 g22.0 g28.0 g44.0 g

5. How much would one mole of CO 2 weigh? 40.0 g22.0 g28.0 g44.0 g Sorry, try again

5. How much would one mole of CO 2 weigh? 40.0 g22.0 g28.0 g44.0 g Sorry, try again

CORRECT! One mole of CO 2 would weigh 44.0 g. Write that answer on your worksheet, and then try the next question g22.0 g28.0 g44.0 g 5. How much would one mole of CO 2 weigh?

6. What would one mole of (NH 4 ) 2 S weigh? 54.1 g38.0 g50.1 g68.1 g

6. What would one mole of (NH 4 ) 2 S weigh? 54.1 g38.0 g50.1 g68.1 g Sorry, try again

6. What would one mole of (NH 4 ) 2 S weigh? 54.1 g38.0 g50.1 g68.1 g Sorry, try again

CORRECT! One mole of (NH 4 ) 2 S would weigh 68.1 g. Write that answer on your worksheet, and then try the next question g38.0 g50.1 g68.1 g 6. What would one mole of (NH 4 ) 2 S weigh?

There is one more important bit of information we need to consider: Seven elements on the periodic table Are not normally found as individual atoms like this: 9 F Cl Br I O N H Instead, they always bonded together into pairs like this:

These seven elements are said to be “diatomic.” And when we write their symbols, we include a subscript “2” after them. Bromine, for example, would not just be “Br.” Instead, it would be “Br 2.” Likewise, oxygen would be “O 2.” 9 F Cl Br I O N H To help remember these seven diatomic elements, just think of the word: Br I N Cl H O F (pronounced “Brinklehof.”) Br O O

The reason that this is important to mention here is that when we talk of “a mole of oxygen,” for example, we are not talking about 6.02x10 23 individual O atoms like this Instead, we are talking about 6.02x10 23 diatomic O 2 molecules, like this 9 F Cl Br I O N H OOOOOOO O O O O O O O O O O O O O O …

That means that one mole of oxygen would not weigh g. It would weigh twice that: g. 9 F Cl Br I O N H O Likewise, one mole of nitrogen would not weigh g. It would weigh twice that: g. 7 N It’s important to keep this in mind when dealing with these seven elements.

Now try problems 7-18 on the mole notesheet. The answers are listed in the margin, so check them off as you do them to make sure you are on the right track.