Stoich project

James Chow 7th Period

What is stoichiometry

Stoichiometry refers to the relationships or ratios between reactants and products. In Greek, it means measuring elements.

Example reaction and information

Potassium chloride bonds with oxygen to form potassium chlorate.

Balanced equation: 2KCl(aq) + 3O2(g) = 2KClO3(aq)

Reaction type: synthesis


KCl: Potassium chloride

O2: Oxygen

KClO3: Potassium chlorate

Molar Masses

Potassium chloride: 74.551 g/mol

Oxygen: 31.98 g/mol

Potassium chlorate: 122.548 g/mol

Proof of reaction

Chemical reaction part 1
Chemical stuff

Mole to mole conversions

In a mole to mole conversion, you only require the given the and coefficients which tell you the ratio between the two reactants/products. You then multiply the given by the ratio.

For example, we have 5.6 moles of KCl and we want to convert it to KClO3. Both of them have a coefficient of 2, so the ratio is 2 to 2. Therefore, KClO3 also has 5.6 moles.

Mass to mass conversions

In a mass to mass conversion, you require the given, molar masses, and coefficients. You first divide the given grams by the molar mass of the reactant/product to find how many moles there are. You then continue the steps from mole to mole conversion. Finally, you multiply it by the molar mass of the second reactant/product.

For example, you have 12.1 grams of KCl and you wish to convert it to KClO3. To solve this, you would divide 12.1 by 74.551, which is the molar mass. Once again the ratio is 2 to 2, so the number stays the same. You now finally multiply by 122.548, which is the molar mass of KClO3. Therefore, the answer is 19.89 grams of KClO3

Limiting and excess reactant

To solve for the limiting and excess reactant, you need to do a mass to mass conversion to the same product for both of them. The limiting reactant is the one who is capable of producing less of the product, or whose answer is smaller. The excess reactant is the one who is capable of producing more product than the other reactant.

For example, you have 12.3 grams of KCl and O2. After working out the mass to mass conversion, KCl can produce 20.219 grams of KClO3 while O2 can produce 31.404 grams of KClO3. Therefore, KCl is the limiting reactant because it can produce less, and O2 is the excess reactant because it can produce more than KCl can.

Theoretical and percent yield

The theoretical yield is how many grams you can produce while the percent yield is the actual yield divided by the theoretical yield times 100. The theoretical yield is the lower number answer from figuring out limiting and excess reactants.

For example, the theoretical yield from the last question is 20.219 grams because you only have enough grams of KCl to produce that much. Even though O2 is capable of producing 31.404, KCl cant produce that much, so the answer will be the 21.219.

Now, lets say your actual yield is 17.359. 17.359 divided by 21.219 x 100 = 85.854. 85.854% is your percent yield.


Stoichiometry: Chemistry for Massive Creatures - Crash Course Chemistry #6