Stoichiometric Calculations

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Foldable

• Obtain 3 sheets of paper.• Stagger the pages about ¾ of an inch.• Fold over so you have multiple flaps.

Titles of Pages

Stoichiometric Calculations

Mole to Mole

Mole to Mass / Mass to Mole

Mass to Mass

Limiting Reactant

Percent Yield

Page 1 - Top

• Open your book, on the top flap, write the following:

• Steps in all stoichiometric calculations:– Write a balanced equation– Identify the known and unknown, what do you

have and what are you trying to find?– Set up the problem with the given information– Identify the mole ratio– Check your answer, does it make sense?

Page 1 – Bottom – Mole to Mole

• Mole of A to Mole of B• Ex. How many moles of H2O are produced from 5.0 moles of H2?

– Balanced Eq: 2H2 + O2 2H2O

– Known: 5.0 mol H2, Unknown: mols of H2O

= 5.00 mol H2O

5.0 mol H2

2 mol H2

2 mol H2O

Mole Ratio

• How many grams of NaCl are produced from 5 moles of Na?

• Balanced Eq: 2 Na + Cl2 2 NaCl

• Known: 5 moles of Na• Unknown: grams of NaCl

Page 2- Bottom – Mass to Mole

Mole of A to Mass of B Mass of A to Mole of B• How many moles of NaCl are

produced from 35 g of Cl2?

• Balanced Eq: 2 Na + Cl2 2 NaCl

• Known: 35 g Cl2• Unknown: moles NaCl

5 mol Na

2 mol Na

2 mol NaCl

1 mol NaCl

58.44 g NaCl

Mole Ratio

= 292.20 g NaCl

35 g Cl270.90 g Cl2

1 mole Cl21 mole Cl2

2 mol NaCl

= 0.99 mol NaCl

Page 3 – Bottom- Mass to Mass• Mass of A to Mass of B• Ex. How many grams of NO2 are produced from 250 g of N2 gas?

• Balanced Eq: N2 + 2O2 2NO2

• Known: 250 g of N2

• Unknown: grams of NO2

= 821.02 g NO2

1 mol N2

28.02 g N2

2 mol NO246.01 g NO2250 g N2

1 mol N2 1 mol NO2

Molar Mass Mole Ratio

Page 4 – Bottom – Limiting ReactantsSame as all the other problems, you just have to do two of them.

• Do the problem with N2 first.

• Balanced Eq: N2 + 2O2 2NO2

• Known: 25 g N2, Unknown: g NO2

= 82.10 g NO2

• Now do the same problem with O2

• Same balanced equation• Known: 35 g O2 ,Unknown: g of NO2

= 50.32 g NO2

If you have 25 g of N2 and 35 g of O2, how many grams of NO2 is produced, which one is the limiting reactant? The excess reactant?

25 g N2

28.02 g N2

1 mol N2

1 mol N2

2 mol NO2

1 mol NO2

46.01 g NO2 35 g O2

32.00 g O2

1 mol O2

2 mol O2

2 mol NO2

1 mol NO2

46.01 NO2

O2 is the limiting reactant, this reactant will determine how much product is made.

NO2 is the excess reactant, it will be left over after the reaction.

50.32 g NO2 is produced

Page 5 – Bottom - % Yield• Ex. Problem: When this experiment

was performed in the lab, the chemist was able to produce 48.45 g of NO2.

• 48.45 g NO2 = actual yield

• %Yield = actual yield

• Done the same way if you need to figure out the amount of product use the limiting reactant steps.

• We will use the same balanced equation: N2 + 2O2 2NO2

• We know that 50.32 g NO2 is produced.

• The amount of product you calculate from the limiting reactant problem is the theoretical yield.

• 50.32 g NO2 = theoretical yield

theoretical yieldX 100

% Yield = 48.45

50.32X 100

= 96.3 %