Mole Calculations & Percent Yield

How many moles are present in 100g of aspirin (C9H8O4, molar mass of 180.2 g/mol)? Round to the correct significant figure.

(Grams → Moles)

0.555 mol

(Rounded to 3 sig figs)

How many molecules are in a 325mg tablet of aspirin (C9H8O4, molar mass 180.2 g/mol)?

(Grams → Molecules)

1.086 X 10 ^ 23

How many molecules are contained in 5.0 moles of carbon dioxide (CO2)?

3.01 X 10 ^ 24

How many moles of CO are produced from 3.5 moles of C2H6? (Mole → Mole)

2 C2H6 + 5 O2 → 4 CO + 6 H2O

7 moles

How many moles of O3 are formed from 9.0 mol of O2? (Moles → Grams)

3 O2 sunlight → 2 O3

288g O3

(290g O3 rounded from sig figs)

Ethanol (C2H6O, molar mass 46.1 g/mol) is synthesized by reacting ethylene (C2H4, molar mass 28.1 g/mol) w/ water. (Grams → Grams)

How many grams of ethanol are formed from 14g of ethylene?

C2H4 + H2O → C2H6O

23g ethanol.

What’s the formula for percent yield?

Percent Yield =

(actual yield / theoretical yield) X 100

If the reaction of ethylene w/ water to form ethanol has a theoretical yield of 23g of ethanol, what’s the percent yield if only 15g are actually formed?

65%

If we are converting grams to molecules, what do we do to convert to molecules from moles?

6.022 X 10 ^ 23 / 1 mol

gK → mol K → mol UK → g UK

Name what each arrow represents.

1st arrow = divide by molar mass

2nd arrow = use molar ratio

3rd arrow = multiply by molar mass