Molar Mass

Introduction to the Mole

with formula writing review

The Mole

• A counting number that equals 6.02 x 10²³ of ANYTHING.

Scientific Notation on Your Calculator

• Use the EE button. It takes the place of (x 10^) in your number. 6.02E23

Multiple Choice

Type this in your calculator: 5 x 6.02E23 and hit enter. What is the answer?

• 3.01E24
• 450000

• 8.3E-24

• 1.2E24

Unit Conversions

• When starting with MOLE you MULTIPLY

  • Use 6.02 x 10²³ when dealing with an amount

  • Use Molar Mass when Dealing with Grams
    

• When starting with atoms/grams you divide

  • Use 6.02 x 10²³ when dealing with an amount

  • Use Molar Mass when Dealing with Grams
    

Molar Mass

• The average atomic mass on the periodic table tells the weighted average of all naturally occurring isotopes. (For an atom in amu.)

• If you have a sample of the element with a mass of that value in GRAMS, you will have exactly one mole of atoms

• 10.81 grams of Boron contains 6.02 x 10²³ atoms of Boron.

Fill in the Blank

One mole of Carbon will weigh ____ grams.

This is true for molecules as well.

• If I have one mole of CO₂ molecules, there will be one mole of C atoms and 2 moles of O atoms. The mass of one mole of CO₂ molecules is (12.011 + 15.999*2) = 44.009 grams.

• We can round to the 10ths place (44.0 g)

Fill in the Blank

What is the molar mass of Aluminum Chloride, AlCl₃?

Fill in the Blank

What is the molar mass for sodium bromide? Round to tenths place

.

Conversion Factors

• 1 mole = 6.02 x 10²³ atoms (molecules, particles, chairs, skittles, etc.)

• 1 mole = molar mass in grams

  • Molar mass comes from the Periodic Table and is different for each element or compound.

You are starting with moles, so you MOLETIPLY. You want grams so you use the molar mass. Do the work and if you miss it ask for help.

​This is a two step problem, starting with grams divide by molar mass to get number of moles. Then multiply by 6.02x10²³ to get atoms. Do the work and ask for help if you miss it

Fill in the Blank

If you have 828.8 grams of Pb how many moles do you have? Round to nearest whole number.

Multiple Choice

9.03 x 10²³ atoms of aluminum will have a mass of ____ grams.

2 step problem

• 19.5

• 400

• .00003

• 5.4 x 10 ²⁵