3.4 Calculating Quantites of Reactant and Product

Question 1

What is true about molar ratios in a balanced equation?

Answer 1

In a balanced equation, the amounts (moles) of substances are stoichiometrically equivalent to each other

Question 2

Steps for solving ANY stoichiometry problem involving a reactant (4 steps)

Answer 2

1. Write the Balanced Equation
2. Convert known mass (or number of entities) of one substance to amount (moles) using its molar mass (or Avogadro’s number)
3. Use the molar ratio to calculate the unknown amount (mole) of the other substance
4. When necessary, convert the amount of that other substance to the desired mass (or number of entities) using its molar mass (or Avogadro’s number)

Question 3

Limiting reactant

Answer 3

amount of mol limiting the other amount of mol that can form

*in equations, the limiting reactant is the one that yields the least quantity of product

Question 4

Excess reactant

Answer 4

the reactant that is not limiting

Question 5

How to determine the limiting reactant (3 steps)

Answer 5

1. Initial quantities of reactants and products before the reaction
2. Change in the quantities of reactants and products during the reaction
3. Final quantities of reactants and products remaining after the reaction

Question 6

Theoretical yield

Answer 6

the amount of product calculated from the molar ratio in the balanced equation
*this is never obtained

Question 7

Actual yield

Answer 7

the amount of product actually obtained

*expressed in units of amount (moles) or mass (grams)

Question 8

Percent yield

Answer 8

actual yield expressed as a percentage of the theoretical yield

Question 9

Equation for Percent Yield

Answer 9

% Yield = (Actual Yield / Theoretical Yield) x 100