Chemical Quantities –Molar Mass

Gram Atomic Mass (gam) = mass of 1 mole of an element.

- basically the atomic mass of an element expressed in grams… How?!?

We know:

1 amu = 1.673 x 10^-24 g

1 atom H = 1 amu

1 mol H = 6.02 x 10²³ atoms of H

1 mol H

1 mol H

6.02 x 10²³ atoms of H

= 1.01 g/mol

1 atom H

1 amu

1.673 x 10^-24 g

1 amu

Gram Atomic Mass (gam)

Ex: H = 1 gam = 1 gram = 1 mol (6.02 x 10²³ atoms of H)

C = 12 gam = 12 grams = 1 mol (6.02 x 10²³ atoms of C)

O = 16 gam = 16 grams = 1 mol (6.02 x 10²³ atoms of O)

Molar Mass = mass (in grams) of one mole a substance.

units = g/mol

1) Add the individual gram atomic mass for each element represented in the chemical formula.

Ex: What is the molar mass of NaOH?

Grams

1 Mole

Mass

Moles

Molar mass allows us to convert between moles and grams!!!

Na= 22.99 g/mol + O= 16.00 g/mol + H= 1.01 g/mol

NaOH= 40.00 g/mol

Na₂OH?

Mass

1 Mole

Ex: A lab group has 175.2 g of CaCl₂. How many moles of CaCl₂ do they have?

Grams

Moles

175.2 g CaCl₂

110.98 g

= 1.579 moles CaCl₂

1 mol CaCl₂

1 Mole

Mass

Mass

1 Mole

Ex: A lab group has .56 mol of Mg(NO₃)₂. How many grams of Mg(NO₃)₂ do they have?

Grams

Moles

.56 mol Mg(NO₃)₂

148.33 g

1 mol Mg(NO₃)₂

= 83 g Mg(NO₃)₂

1 Mole

Mass

Mass

1 Mole

COMPLETE OVERVIEW OF MOLE PROBLEMS

Grams

Moles

R.P.

Molecule

Atom

Chemical Formula

1 Mole

Mass

Mass

1 Mole

6.02 x 10²³

1 Mole

1 Mole

6.02 x 10²³