• Volume– Gas is $4.00 a gallon

• Mass– Apples are $1.49 a pound

• Count– Bananas are $0.79 each

How do we measure?

Certain words represent a number• Dozen = ?

• Couple = ?

• Score = ?

• Mole = ?

What is a Mole?

What is a Mole?

• A number of particles• 1 mole = 6.02x1023

• This is Avagadro’s Number

Conversion Problems…Dozen = 12 so…… 1 Dozen = 12 = 1

12 1 Dozen

1 mole = 6.02x1023 so…..

1mole = 6.02x1023 particles = 1 6.02x1023 particles 1 mole

Problems

①How many eggs are in 5.5 dozen?

②How many years is “four-score and seven years”? (Do you know who said this?)

Problems

①How many moles are in 3.80 x 1024 atoms of Ca?

②How many molecules are in 0.280 mole of H2O?

Skittles• How may schools could 1 mole of skittles fill?

1 liter = 1340 skittles1 box = 28.4 liters1 room = 14,000 boxes1 school = 500 rooms

The Mass of a Mole of an Element• Molar Mass: The mass of a mole of an element– Look at the Periodic Table

1 mole Carbon = 12.01g

What is the molar mass of….

①Oxygen =

②Sulfur =

③Iron =

④Sodium =

The Mass of a Mole of a Compound

• Molar mass of a compound: 1) Find the number of grams of each element in the

compound2) Add the masses of all the elements in the

compound

What is the molar mass of….

①H2O =?

②SO3 = ?

③NaCl = ?

Counting by measuring mass lab

• Paper Clips - Pg 286

• Each group turns in 1 paper with your data and questions 1-3.

Mole – Mass Relationship

• Convert between the mass of a substance and the moles of a substance using the molar mass

mass (grams) = # of moles x mass (grams)1 mole

moles = mass (grams) x 1 mole mass (grams)

Mass & Moles Problems

① What is the mass of 3 mol of NaCl?

mass NaCl = ______ x _______ = ______

②How many moles of (Fe2O3) are in a 92.2 g sample?

mol (Fe2O3) = ________ x ________ = _______

Percent Composition of a CompoundPercent Composition: Percent (by mass) of each

element in a compound

% mass of element = mass of element x 100% mass of compound

What is the percent composition of…

①A 13.60g sample containing only Mg and O is decomposed and 5.4g O2 is obtained. What is the percent composition of the original compound?

Percent Composition• If you don’t know the mass of the compound, use

the molar mass:

% mass = mass of element in 1 mol compound x 100% molar mass of compound

①What is the percent composition of H2O?

Percent Composition①Calculate the amount of carbon in 2.56g Na2CO2

Popcorn Lab1. How many grams of water are in a kernel (average)?2. What is the percent composition of water in an kernel? 3. How many moles of water (on average) are in a kernel?4. How many moles of oxygen?5. How many moles of hydrogen?6. How many atoms of oxygen?7. How many atoms of hydrogen?8. How many grams of oxygen?9. How many grams of hydrogen?10. What is the percent composition of water (what percent

by mass is H, O?)

Mole – Volume Relationship

• Avogadro’s hypothesis: equal volumes of gases at the same temperature and pressure contain equal numbers of particles– Standard Temperature and Pressure (STP):• Temperature = 0°C• Pressure = 1 atmosphere (atm) or 101.3 kPa

– Molar Volume = 22.4L

Mole – Volume Relationship

Mass – Volume Relationship

Volume of gas = moles of gas x 22.4 L1 mole

①What is the volume of 0.6 mol SO2 at STP?

②How many moles of O2 gas are in 0.4L at STP?

Moles!

MolarityCalculating Concentrations

• Molarity = Number of mol of soluteNumber of L of solution

• Solute = The Dissolved Substance• Ex: Sugar, Salt

• Solvent: The Dissolving Medium• Ex: Water

Calculating Concentrations

• A saline solution contains 0.90g NaCl in exactly 100mL of solution. What is the molarity of the solution?

Calculating Concentrations

1. How many moles of solute are present in 1.5L of 0.70M NaClO? (bleach)

If you were to add solvent to the solution, what would happen to the molarity?

Parts Per Million (ppm)Calculating Concentrations

• One part per million parts

1ppm = 1mg of solute 1 L of solution

Because 1mL of water = 1mgSo 1L of water would be 1,000,000mg.

Empirical Formulas

• The lowest whole-number ratio of elements in a compound Ex: empirical formula

C2H2 CH

C4H4 CH

C8H8 CH

What is the empirical formula…① A compound is 25.9% nitrogen and 74.1% oxygen. What is

the empirical formula? (Hint: Remember, percent composition is MASS)

1. Assume the compound is 100g.2. Change ratio of masses to moles.

3. Reduce ratio to lowest whole-number ratio by dividing by molar quantity with smaller number of moles.

4. If ratios are still not a whole number, multiply each part of the ratio that will convert both to whole numbers

What is the empirical formula of…

①A compound that is 94.1% oxygen and 5.9% hydrogen.

Molecular FormulasEither:

-the same as the empirical formula-a simple whole-number multiple of the

empirical formula.

Empirical Formula Molecular FormulaCH2O CH2O

CH2O x 2 C2H4O2

CH2O x 6 C6H12O6

①Calculate the molecular formula of a compound whose molar mass is 60.0g/mol and empirical formula is CH4N.

1. Calculate the mass of the empirical formula.

2. Divide the molar mass by the mass of the empirical formula to find a whole number

3. Multiply the subscripts by the whole number found

①Find the molecular formula of ethylene glycol (used in antifreeze). The molar mass is 62g/mol and the empirical formula is CH3O.