This document provides instructions and examples for calculating molar mass, determining the number of moles, calculating percent composition to determine an empirical formula, and using the empirical formula to determine the molecular formula. It outlines the step-by-step processes for performing mole calculations and conversions between grams, moles, molecules and volume. Practice problems are provided for calculating molar masses, determining moles from mass, calculating empirical formulas from elemental analysis, and determining molecular formulas from empirical formulas and molar masses.

1. Chapter 10 Notes—ALL ABOUT THE MOLE!
How do I calculate molar mass?
STEP 1:
STEP 2:
STEP 3:
STEP 4:
What is a mole?
TRY IT OUT!
Find the molar masses of:
NaCl H2
O
SO3
PCl3
MOLAR MASS!

2. EVERYTHING GOES THROUGH THE MOLE!
WHAT IS A TWO-STEP CONVERSION PROBLEM?
Calculate the number of molecules in 60.0 g NO2.
1st
Conversion:
2nd
Conversion:
So here’s an example!
Here’s the equation:

3. How many moles is 2.80 X 1024
atoms of silicon?
How many moles is 2.17 X 1023
particles of bromine?
How many moles are in 20 grams of NaCl?
Determine the volume in liters of 5 moles of hydrogen gas.
Another example:
Calculate the volume, in liters, of 3.24 x 1022 molecules of Cl2 (STP).
LET’S PRACTICE!

4. Calculating Percent Composition
Step 1:
Step 2:
Step 3:
Step 4:
Let’s Practice:
What is the percent composition of PbCO 4 ?
• When no formula is given, take the numbers that are given and add them together
to get a total.
• Divide each number by the total and multiply by 100 to get the percent.
EMPIRICAL FORMULA
• What is an empirical formula?

5. • This is a formula that gives the lowest whole number ratio of atoms in a
compound.
• It’s similar to reducing fractions.
Calculating Empirical Formula
Step 1:
Step 2:
Step 3:
Step 4:
Step 5:

6. Let’s Practice:
A compound is analyzed and found to contain 13.5 g Ca, 10.8 g O and .675 g H. What is
the empirical formula of the compound?
Molecular Formula
• Molecular formula is similar to empirical formula.
• It is a multiple of the empirical formula and reflects the actual chemical formula.
Step 1:
Step 2:
Step 3:
Step 4:

7. Let’s Practice!
A compound with the empirical formula of C2OH4 has a molar mass of 88 grams per
mole. What is its molecular formula? Hint: the empirical formula has already been
calculated for you.
Topics on the test:
*Calculate molar mass
*Convert Moles, liters, grams and molecules/atoms using mole road.
*Calculate percent composition
*Calculate empirical formula
*Calculate molecular formula