10-1: THE MOLE You will need your calculator EVERY DAY!!!!!!!!!!!

The Mole 1. Avogadro’s Number (aka the MOLE): A MOLE of something (cars, bananas, atoms, molecules, people) is 6.02 x A MOLE of something (cars, bananas, atoms, molecules, people) is 6.02 x This concept is similar to the idea of a “dozen” being equal to 12 things (eggs, cookies, etc) This concept is similar to the idea of a “dozen” being equal to 12 things (eggs, cookies, etc) Because atoms are so small, it takes a huge number of them to make up a visible amount. The mole allows us to talk about the number of atoms in a sample we have. Because atoms are so small, it takes a huge number of them to make up a visible amount. The mole allows us to talk about the number of atoms in a sample we have.

2. Where did chemists come up with that random number? Named after the man who founded it (Avogadro) Named after the man who founded it (Avogadro) In carbon-12 (i.e. C with 6 protons and 6 neutrons, which has an atomic mass of 12 amu), there are 6.02 x C atoms in 12 grams. In carbon-12 (i.e. C with 6 protons and 6 neutrons, which has an atomic mass of 12 amu), there are 6.02 x C atoms in 12 grams. Said another way, one mole of C atoms is 12 grams Said another way, one mole of C atoms is 12 grams The mole allowed chemists to talk about how much of an element they have in grams The mole allowed chemists to talk about how much of an element they have in grams

3. How big is Avogadro’s the number? Why is it so big? If you stacked a mole of sheets of paper on top of each other, the stack would reach beyond the solar system If you stacked a mole of sheets of paper on top of each other, the stack would reach beyond the solar system This number is so large so we can reasonably talk about a HUGE amount of really tiny atoms This number is so large so we can reasonably talk about a HUGE amount of really tiny atoms

Working with the mole… First, let’s look at something familiar… First, let’s look at something familiar… 4. Let’s say I have a dozen bikes. How many wheels do I have? How many dozen wheels do I have? 5. Let’s say I have one mole of bikes. How many moles of wheels do I have? 6.How many wheels do I have in 1 mole of bikes?

ANSWERS First, let’s look at something familiar… First, let’s look at something familiar… 4. Let’s say I have a dozen bikes. How many wheels do I have? How many dozen wheels do I have? 2 dozen wheels or 24 wheels 5. Let’s say I have one mole of bikes. How many moles of wheels do I have? 2 moles of wheels 6.How many wheels do I have in 1 mole of bikes? 2 moles wheels x (6.02 x ) = 1.2 x mole 1 mole

Now let’s talk about atoms… A: How many atoms/ions are in a compound? Look at the subscripts and add the total number of elements together. If necessary, multiply by the total # of ions/elements. Look at the subscripts and add the total number of elements together. If necessary, multiply by the total # of ions/elements. Example: How many ions are there in the compound CaCl 2 ? Example: How many ions are there in the compound CaCl 2 ? How many Cl ions are in the compound? How many Cl ions are in the compound? If I have 12 CaCl 2 compounds, how many Cl ions do I have? If I have 12 CaCl 2 compounds, how many Cl ions do I have?

Example: How many ions are there in the compound CaCl 2 ? Example: How many ions are there in the compound CaCl 2 ? Ca + Cl + Cl = 3 How many Cl ions are in the compound? How many Cl ions are in the compound? Cl + Cl = 2 If I have 12 CaCl 2 compounds, how many Cl ions do I have? If I have 12 CaCl 2 compounds, how many Cl ions do I have? CaCl 2 CaCl 2 CaCl 2 CaCl 2 CaCl 2 CaCl 2 CaCl 2 CaCl 2 CaCl 2 CaCl 2 CaCl 2 CaCl 2 OR 12 X 2 = 24 Cl atoms

B. How many moles of each type of atom/ion do I have? Multiply the number of moles by the subscript Multiply the number of moles by the subscript Example: How many moles of Cl are in 5 moles of the compound CaCl 2 ? Example: How many moles of Cl are in 5 moles of the compound CaCl 2 ? How many moles of Cl atoms are in ONE mole? How many moles of Cl atoms are in ONE mole? Multiply by how many moles you have: Multiply by how many moles you have:

B. How many moles of each type of atom/ion do I have? Example: How many moles of Cl are in 5 moles of the compound CaCl 2 ? Example: How many moles of Cl are in 5 moles of the compound CaCl 2 ? How many MOLES of Cl atoms are in ONE mole? How many MOLES of Cl atoms are in ONE mole? 2 atoms per compound  2 moles Cl per mole Multiply by how many moles you have: Multiply by how many moles you have: 10 moles Cl

C. How many atoms/ions do I have? Multiply the number of MOLES of the atom by Avogadro’s number. Example: How many ions of Cl are in 5 moles of compound CaCl 2 ? Example: How many ions of Cl are in 5 moles of compound CaCl 2 ? First find the total # of moles of Cl: First find the total # of moles of Cl: Use Avogadro’s number as a conversion factor: Use Avogadro’s number as a conversion factor: 6.02 x mole (cancel units you don’t want) 1 mole (cancel units you don’t want)

C. How many atoms/ions do I have? Multiply the number of MOLES of the atom by Avogadro’s number. Example: How many ions of Cl are in 5 moles of compound CaCl 2 ? Example: How many ions of Cl are in 5 moles of compound CaCl 2 ? First find the total # of moles of Cl: First find the total # of moles of Cl: 10 moles Cl Use Avogadro’s number as a conversion factor: Use Avogadro’s number as a conversion factor: 6.02 x mole (cancel units you don’t want) 1 mole (cancel units you don’t want) 10 moles Cl x 6.02 x = 6.02 x Cl atoms 10 moles Cl x 6.02 x = 6.02 x Cl atoms 1 mole 1 mole