Moles and Molar Mass

Calculating Molar Mass of a Compound

• Determine the number of atoms of each element

• Multiply the number of atoms by the atomic mass of each element

• Add the molar masses of each element together for the molar mass of the compound

Multiple Choice

Which BEST describes what the unit of mole can be used for? 

• To measure the amount of grams in a substance

• To measure the amount of atoms or molecules in a substance

• To measure the amount of energy in a substance

• To measure the amount of bonding in a substance 

Multiple Choice

How many Oxygen atoms are in the compound Ba₃(PO₄)₂

• 4

• 8

• 6

• 3

Multiple Choice

What are the units for molar mass?

• grams

• amu

• grams/mole

• liters

Multiple Choice

The molar mass of an element is equal to its...

• Atomic mass

• Atomic number

• Oxidation number

• Valence electrons

Multiple Choice

What is the molar mass of phosphorus?

• 123.88 g

• 30.97 g

• 123.88 g/mol

• 30.97 g/mol

Reorder

Reorder the following in the order of steps on calculating molar mass

• Count the # of atoms of each element

• Use the periodic table to determine the mass of each element

• Multiply the number of atoms of each element by their mass

• add all of the different amounts

1

2

3

4

• 1
• 2
• 3
• 4

Multiple Choice

Calculate the molar mass of AuCl₃

• 96 g

• 130 g

• 232.5 g

• 303.3 g

Multiple Choice

In chemistry, a "mole" is:

• The mass of an atom

• a large number used to count particles

• based on the volume of a substance

Multiple Choice

Calculate the moles in 12.7g of CaF₂

• 0.20 mol

• 1,000.76 mol

• 6.14 mol

• 0.16 mol

Multiple Choice

What is the molar mass of Sr(NO₃)₂?

• 211.64 g/mol

• 163.64 g/mol

• 149.63 g/mol

• 197.63 g/mol

Multiple Choice

Which would have more atoms?

• 1 mole of Li

• 1 mole of Au

• 1 mole of Si

• None, all are equal

Mole Conversions

#2 Mass and Moles

Mass & Moles

●

1 mole = molar mass (g), calculate from PTE.

●

To convert from…

○

moles to mass, multiply by molar mass

○

mass to moles, divide by molar mass

Example: What is the mass of 0.82 moles of lithium
carbonate, Li2CO3?

Moles to Mass

Multiply moles by molar mass.

Example: How many moles are in 2.3 g sodium chloride,
NaCl?

Mass to Moles

Divide mass by molar mass.

Conversion tips

• The unit you are looking for always goes on the top of the conversion factor

• If both numbers are on the top multiply them

• If one number is on the top and one is on the bottom divide.

Multiple Choice

What is the mass of 0.89 mol of CaCl₂?

• 111 grams

• 0.008 grams

• 98.9 grams

• none of the choices

Multiple Choice

How many moles are in 100.0 g of dinitrogen oxide (N₂O)?

• 2.272 mol N₂O

• 6.25 mol N₂O

• 7.14 mol N₂O

• 44.013 mol N₂O

Multiple Choice

How many grams are in 2.40 mol of sulfur?

• 9.35 x 10^-3 g

• 77.0 g

• 616 g

• 0.0748 g

Multiple Choice

A mass of 6 g of Carbon contains

• 1 mole of C

• 2 moles of C

• 0.5 moles of C