Chapter 7 Chemical Quantities or

How do you measure how much? You can measure mass, volume, or you can count pieces of a substance. We measure mass in grams. We measure volume in liters. We count pieces in MOLES. No, not that kind of mole!!!

Moles Defined as the number of carbon atoms in exactly 12 grams of carbon mole is 6.02 x particles. Treat it like a very large dozen x is called Avogadro's number. The units of Avogadro’s number can be whatever particle you are counting. – Examples: atoms, molecules, ions, formula units, etc… – In chemistry these are called Representative Particles

What are Representative Particles? The smallest pieces of a substance. For an element it is an atom. – Unless it is diatomic For a covalent compound it is a molecule. For an ionic compound it is a formula unit. If it has a charge, it is an ion.

How do We Use Moles? Moles are used as conversion factors. This means they are used to change units. Remember, when solving using conversion factors there are 3 questions you want to ask yourself: – What unit do you want to get rid of? – Where does it go to cancel out? – What can you change it into?

Calculation question 1 How many molecules of CO 2 are the in 4.56 moles of CO 2 ? Answer: 2.75 x molecules of CO 2

Calculation question How many moles of water is 5.87 x molecules of water? ANSWER: moles of water

Calculation question How many molecules of sugar are there in 1.23 moles of C 6 H 12 O 6 ?

Measuring Moles The atomic mass unit (amu) is one twelfth the mass of a carbon 12 atom. Since the mole is the number of atoms in 12 grams of carbon-12, the decimal number on the periodic table is: – The mass of the average atom in amu. This mass is equivalent to the mass of 1 mole of those atoms in grams.

Gram Atomic Mass The mass of 1 mole of an element in grams grams of carbon has the same number of pieces as grams of hydrogen and grams of iron. We can write this as g C = 1 mole We can count things by weighing them.

Examples How much would 2.34 moles of carbon weigh? 28.1 grams of C How many moles of magnesium in 4.61 g of Mg? moles of Mg

What about compounds? In 1 mole of H 2 O molecules there are two moles of H atoms and 1 mole of O atoms To find the mass of one mole of a compound: – Determine the moles of the elements they have – Find out how much their mass is by using the periodic table and then add them up

Example What is the mass of one mole of CH 4 ? 1 mole of C = g 4 mole of H x 1.01 g = 4.04g 1 mole CH 4 = = 16.05g The Gram Molecular mass of CH 4 is 16.05g

Gram Molecular Mass or GMM The mass of one mole of a molecular compound. Gram Formula Mass - The mass of one mole of an ionic compound. Calculated the same way as GMM. What is the GFM of Fe 2 O 3 ? 2 moles of Fe x g = g 3 moles of O x g = g The GFM = g g = g

Molar Mass The generic term for the mass of one mole. The same as gram molecular mass, gram formula mass, and gram atomic mass. This is the term we will be using in class. I do NOT weigh that much! The balance must be lying!!!

Examples Calculate the molar mass of the following and tell me what type it is (gmm, gfm, or gam). Na 2 S N 2 O 4 C Ca(NO 3 ) 2 C 6 H 12 O 6 (NH 4 ) 3 PO g/mol g/mol g/mol g/mol g/mol g/mol

Using Molar Mass Finding moles of compounds Counting pieces by weighing

Molar Mass The number of grams in 1 mole of atoms, formula units, or molecules. We can make conversion factors from these. It will allow us to change grams of a compound to moles of a compound. Or moles to grams.

For example How many moles is 5.69 g of NaOH?

For example How many moles is 5.69 g of NaOH?

For example How many moles is 5.69 g of NaOH? l need to change grams to moles

For example How many moles is 5.69 g of NaOH? l need to change grams to moles for NaOH

For example How many moles is 5.69 g of NaOH? l need to change grams to moles for NaOH l 1mole Na = 22.99g 1 mol O = g 1 mole of H = 1.01 g

For example How many moles is 5.69 g of NaOH? l need to change grams to moles for NaOH l 1mole Na = 22.99g 1 mol O = g 1 mole of H = 1.01 g add these together to get the molar mass – use it to convert! l 1 mole NaOH = g

For example How many moles is 5.69 g of NaOH? l need to change grams to moles for NaOH l 1mole Na = 22.99g 1 mol O = g 1 mole of H = 1.01 g l 1 mole NaOH = g

For example How many moles is 5.69 g of NaOH? l need to change grams to moles for NaOH l 1mole Na = 22.99g 1 mol O = g 1 mole of H = 1.01 g l 1 mole NaOH = g

Examples How many moles is 4.56 g of CO 2 ? How many grams is 9.87 moles of H 2 O? mol CO g H 2 O

Gases and the Mole Where is my air tank?? I hope it’s filled to 22.4 L

Gases Many of the chemicals we deal with are gases. They are difficult to weigh, so we’ll measure volume. We still need to know how many moles of gas we have. Two things affect the volume of a gas: – Temperature and pressure. So we have to compare at the SAME temp. and pressure.

Standard Temperature and Pressure Avogadro's Hypothesis - at the same temperature and pressure equal volumes of gas have the same number of particles. 0ºC and 1 atm pressure abbreviated STP At STP, 1 mole of gas occupies 22.4 L Called the molar volume

Examples What is the volume of 4.59 mole of CO 2 gas at STP? How many moles is 5.67 L of O 2 at STP? What is the volume of 8.8g of CH 4 gas at STP?

We have learned how to change moles to grams moles to atoms moles to formula units moles to molecules moles to liters

Volume Molecules Atoms Representative Particles Mass PT Moles 6.02 x L Count