What is the average mass of one water molecule?

2 H atoms x 1.01 u = 2.02 u

1 O atom x 16 u = 16.00 u

2.02 u + 16.00 u = 18.02 u for H2O

The Molar Mass of a compound is numerically equal to its formula mass

In H2O we have two moles of hydrogen and one mole of oxygen

What is the molar mass of one water molecule?

2 H moles x 1.01 g = 2.02 g

1 O mole x 16 g = 16.00 g

2.02 g + 16.00 g = 18.02 g/mol for H2O

Molar Mass

What is the molar mass of barium nitrate, Ba(NO3)2?

Molar Mass is used to convert from Moles to Grams

amount in moles x molar mass = mass in grams

What is the mass in grams of 2.50 mol of oxygen gas?

Percentage Composition

Find the percentage composition of copper(I) sulfide, Cu2S.

Formula Mass

Find the formula of potassium chlorate, KClO3

Percent Composition is the number of grams in one mole of a compound

You can find out how much one element contributes to the overall makeup of a compound:

mass of element in compound / total mass of compound x 100

**6.3 Using Chemical Formulas**

**Ch. 6 Chemical Formulas and Chemical Compounds**

Formula Mass Practice F

1a. 98.09 u

1b. 164.10 u

1c. 94.97 u

1d. 95.21 u

Molar Mass Practice G

1a. 2 mol Al, 3 mol S

1b. 1 mol Na, 1 mol N, 3 mol O

1c. 1 mol Ba, 2 mol O, 2 mol H

2a. 150.17 g/mol

2b. 85.00 g/mol

2c. 171.35 g/mol

Molar Mass as a Conversion Factor Practice

What is the mass in grams of 3.04 mol of ammonia vapor, NH3?

Calculate the mass of 0.257 mol of calcium nitrate, Ca(NO3)2.

51. 8 g

42.2 g

Molar Mass as a Conversion Factor

Ibuprofen, C13H18O2, is the active ingredient in many nonprescription pain relievers. Its molar mass is 206.31 g/mol. If the tablets in a bottle contain a total of 33 g of ibuprofen, how many moles of ibuprofen are in the bottle? How many molecules of ibuprofen are in the bottle? What is the total mass in g of C in 33 g of ibuprofen?

Molar Mass as a Conversion Factor Practice I

1a. 0.0499 mol

1b. 61 mol

2a. 1.53 x 10^23 molecules

2b. 2.20 x 10^23 molecules

3. 1170 g

Calculate the percentage composition of sodium nitrate, NaNO3

Calculate the percentage composition of silver sulfate, Ag2SO4

Percentage Composition Practice

27.05% Na, 16.48% N, 56.47% O

69.19% Ag, 10.28% S, 20.52% O

Percentage Composition K

As some salts crystallize from a water solution, they bind water molecules in their crystal structure. Sodium carbonate forms such a hydride, in which 10 water molecules are present for every formula unit of sodium carbonate. Find the mass percentage of water in sodium carbonate decahydrate, Na2CO3x10H2O, which has a molar mass of 286.19 g/mol.

Percentage Composition Practice K

1a. 74.51% Pb, 25.49% Cl

1b. 52.55% Ba, 10.72% N, 36.73% O

2. 46% H2O

3. 96.0 g O, 6.00 mol O