Moles Part 2 – Mass in a Mole

Aim CE4:What is the mass of a mole of water?

•How much mass is in a mole of a chemical formula?

•It varies, depending on:o The elements in the moleo The ratio of elements in the mole

•The Atomic Mass in the Periodic Table gives us the mass of one atom

•It is also EQUIVALENT (not equal) to the mass of 1 mole of that atom in GRAMS

•Example: o The mass of 1 atom of lithium is 6.941 amu’so The mass of 1 mole of lithium is 6.941 grams

What is the gram formula mass (GFM)?

•It is the sum of all the masses of the elements in a compound or element

•1 mole of H2O = 2 moles H2 + 1 mole O2

•2 mole of H2 x 1.01 grams = 2.02 grams

1 mole

•1 mole of O2 x 16.0 grams = 16.0 grams

1 mole

•2.02 g H2 + 16.0 g O2

= 18.02 g H2O

Practice: what is the gram formula mass of 1 mole of each of the following?1. Iron (Fe) = _________

2. Chlorine (Cl2) = _________

3. Sodium chloride (NaCl) = _________

4. Hydrogen peroxide (H2O2) = ___________

5. Magnesium nitrate (Mg(NO3)2) = __________

Gram Formula Mass Calculations

• How do we determine the number of moles in a given number of grams?

• Mole Calculations, Table Tnumber of moles = given mass

gram-formula mass (gfm)

• A chemist has exactly 46.0 grams of Na available to react. How many moles of Na does she have? (gfm of Na = 23.0g/mole)

number of moles = 46.0 g Na given 23.0 g Na/mole

= 2.00 moles Na

Practice:• How many moles are in 27.0 grams of

water? (GFM = 18.0 g/mole)

• How many grams are in 3.00 moles of sodium chloride? (GFM = 58.5 g/mole)

• How many moles are in 150.5 grams of KNO3?

• How many grams are in a 1.80 gram sample of water?