Stoichiometry Review

Stoichiometry Review Flashcards

Reactant

The substance on the left side of the arrow in a chemical equation; what goes into the reaction.

Product

The substance on the right side of the arrow in a chemical equation; what comes out of the reaction.

Molar mass

The mass of 1 mole of a substance, which is the average atomic mass in grams on the Periodic Table.

Mole ratio

A fraction made from the coefficients of the balanced equation, used to convert between moles of different substances. (want/cancel)

Limiting Reactant

The reactant that is completely consumed first in a chemical reaction, determining the maximum amount of product that can be formed.

Excess Reactant

The reactant that is left over after the limiting reactant is completely consumed in a chemical reaction.

Actual Yield

The measured amount of product actually produced in a chemical reaction.

Theoretical Yield

The calculated amount of product that should be produced based on the stoichiometry of the reaction.

Percent Yield

The ratio of the actual yield to the theoretical yield, expressed as a percentage. Calculated as (actual / theoretical) x 100.

Law of Conservation of Mass

The principle that mass cannot be created nor destroyed in a chemical reaction.

Grams to Moles Conversion

To convert grams to moles, multiply the given grams by (1 mole / molar mass).

Mole to Mole Problem

Multiply the given moles by a fraction made from the balanced equation with what you want on top with its coefficient and what you are canceling out on the bottom with its coefficient.

Finding the Limiting Reactant

Take the moles given of each reactant (If grams, then make moles) and divide each by the coefficient for that reactant. The smaller answer is the limiting reactant. The other is the excess reactant.

Gram to Gram Problem Steps

1. Turn given grams to moles (1 mole / molar mass). 2. Use mole ratio to turn moles of given into moles of what you want. 3. Turn mole of what you want into grams of what you want (molar mass / 1 mole).

Law of Conservation of Mass Application

The grams of reactants don’t equal the grams of product then the difference between those two values is the grams of left over excess reactant.

Reason Percent Yield Seldom 100%

To get 100% yield, ALL of both reactants have to bump into each other. This is hard to do in reality because the products that are forming get in the way.