Molar Mass

1
Molar Mass

• Sections 4-4 to 4-6

2
Carbon

• Atomic is 6
• Atomic mass is 12.01 u
• Molar mass (mass per mole) is 12.01
  g/mole

3
Molar Mass

• Molar mass for an element is found by taking the
  atomic mass for that element in the periodic
  table and changing the units to grams/mole.
• Molar mass for a compound is found by adding the
  atomic masses (in grams) for ALL the elements in
  the compound.

4
H2O

• Molar mass of hydrogen is 1.01g/mole
• There are two atoms of hydrogen in water
• Molar mass of oxygen is 16.0 g/mole
• 2(1.01 g/mole) H 16.0 g/mole O
• 18.02 g/mole H2O

5
NaCl

• Molar mass of sodium is 22.99 g/mole
• Molar mass of chlorine is 35.45 g/mole
• 22.99 g/mole Na 35.45 g/mole Cl
• 58.44 g/mole NaCl

6
What is the mass of 1.31 mol of silver nitrate?

• Find the correct chemical formula for silver
  nitrate.
• silver Ag
• nitrate NO3-
• Silver nitrate is AgNO3

7

• 2. Find the molar mass of AgNO3.
• molar mass Ag 107.87 g/mole
• molar mass N 14.01 g/mole
• molar mass O 16.00 g/mole
• there are three atoms of O
• 107.87 g/mole Ag 14.01 g/mole N
• 3(16.00 g/mole O) 169.88 g/mole AgNO3

8

• Find the mass of 1.31 mole of AgNO3.
• X g AgNO3 169.88 g AgNO3
• ______________ ______________
• 1.31 mole AgNO3 1 mole AgNO3
• X 222.54 g AgNO3

9
How many moles are in a 124 g sample of C8H18?

• Find the molar mass of C8H18.
• molar mass C 12.01 g/mole
• there are 8 atoms of C
• molar mass H 1.01 g/mole
• there are 18 atoms of H
• 8(12.01 g/mole C) 18(1.01 g/mole H)
• 114.26 g/mole C8H18

10

• 2. Find how many moles of C8H18 are in 124.0
  grams.
• x moles C8H18 1 mole C8H18
• _____________ ____________
• 124.0 g C8H18 114.26 g/mole C8H18
• x 1.09 moles C8H18

11

• Copy the Molar Calculator from either the poster
  on the wall, or from page 108 in the text book.
• Do practice questions on page 109 4-8,
• 10-11, 13-16.
• These practice questions will be corrected in
  class on Thursday.