Molecular Mass Elements Single elements by themselves Example

Molecular Mass

Elements • Single elements by themselves – Example: Sodium Na • 1 mole = 6 x 1023 atoms – 1 mole Na = 6 x 1023 atoms of Na • 1 mole = atomic weight in grams – 1 mole Na = 23 grams Na

Compounds • More than one element chemically combined – Example: Na 2(SO 4) • 1 mole = 6 x 1023 molecules – 1 mole Na 2 SO 4 = 6 x 1023 molecules Na 2 SO 4 • 1 mole = molecular weight in grams – 1 mole Na 2 SO 4 = (2 x 23) + (1 x 32) + (4 x 16) = 142 grams

Dimensional Analysis • If you had 5 grams of Na, how many moles do you have? 1. Identify what is given to you. - 5 grams Na 2. Identify what you are trying to find. - moles of Na

Dimensional Analysis • If you had 5 grams of Na, how many moles do you have? 3. Identify the correct conversion factor. 1 mole of Na, =23 grams, therefore 1 mole Na 23 grams OR 23 grams 1 mole Na

Dimensional Analysis • If you had 5 grams of Na, how many moles do you have? 4. Calculate the answer. 5 grams Na 1 mole Na 23 grams Na = 0. 217 moles Na

Dimensional Analysis • If you had 5 grams of Na 2 SO 4, how many moles do you have? 1. Identify what is given to you. - 5 grams Na 2 SO 4 2. Identify what you are trying to find. - moles of Na 2 SO 4,

Dimensional Analysis • If you had 5 grams of Na 2 SO 4, how many moles do you have? 3. Identify the correct conversion factor. 1 mole of Na 2 SO 4, =142 grams, therefore 1 mole Na 2 SO 4, OR 142 grams 1 mole Na 2 SO 4,

Dimensional Analysis • If you had 5 grams of Na 2 SO 4, how many moles do you have? 4. Calculate the answer. 5 grams Na 2 SO 4 1 mole Na 2 SO 4, = 0. 035 mol Na 2 SO 4 142 grams Na 2 SO 4