Practice: AP Chemistry stoichiometry limiting reactant

What is stoichiometry?

The calculation of reactants and products in chemical reactions using balanced equations.

Define limiting reactant.

The reactant that is completely consumed first, limiting the amount of product formed.

What is the purpose of a balanced equation?

To ensure the law of conservation of mass is followed; atoms are neither created nor destroyed.

True or false: Excess reactant is completely used up.

False, because excess reactant remains after the reaction.

Calculate moles of O₂ from 2 moles of H₂.

$\displaystyle 2H₂ + O₂ → 2H₂O$ yields 1 mole of O₂ for every 2 moles of H₂.

Difference between theoretical yield and actual yield?

Theoretical yield is the maximum possible product, while actual yield is the measured amount produced.

What unit measures moles?

Moles are measured in units of substance, represented by Avogadro's number: $\displaystyle 6.022 \times 10^{23}$.

Fill in the blank: The _____ ratio relates moles of reactants to products.

stoichiometric

What is a mole ratio?

A ratio derived from the coefficients of a balanced chemical equation, used in stoichiometric calculations.

Given 5 moles of A and 6 moles of B, which is limiting?

Depends on the reaction equation; need stoichiometric coefficients to determine.

True or false: All reactants in a reaction are limiting.

False, only one reactant can be limiting in a specific reaction.

How to find limiting reactant?

Calculate the amount of product each reactant can produce; the one that produces less is limiting.

What is percent yield?

The ratio of actual yield to theoretical yield, expressed as a percentage: $\displaystyle \\frac{actual \ yield}{theoretical \ yield} \times 100$.

Fill in the blank: The _____ is the leftover substance after a reaction.

excess reactant

What happens if the limiting reactant is increased?

Additional product can be formed only if other reactants are also available in sufficient amounts.

True or false: Stoichiometry applies only to gas reactions.

False, stoichiometry applies to reactions in all states (solid, liquid, gas).