Stoichiometry Basics
What is stoichiometry?
The calculation of reactants and products in chemical reactions.
What is the limiting reactant in a chemical reaction?
The reactant that runs out first, limiting the amount of product.
What is the formula for percent yield?
(Actual yield / Theoretical yield) × 100%.
How many moles of H₂O are produced when 4 moles of H₂ react with excess O₂?
4 moles of H₂O
If 10.0g of Al reacts with 19.7g of Cl₂, what is the limiting reactant? (2Al + 3Cl₂ → 2AlCl₃)
Al (aluminum).
If the theoretical yield of CO₂ is 50g but only 42g is produced, what is the percent yield?
84%
Convert 36.0 grams of H₂O to moles.
2 moles H₂O (36.0 g ÷ 18.0 g/mol).
True or False: The excess reactant is completely used up in a reaction.
False.
If a reaction is expected to produce 25g of product but only makes 20g, is the percent yield greater or less than 100%?
less than 100%
If 3 moles of CH₄ react with excess O₂, how many moles of CO₂ are produced? (CH₄ + 2O₂ → CO₂ + 2H₂O)
3 moles CO₂.
If 4 moles of N₂ react with 10 moles of H₂ (N₂ + 3H₂ → 2NH₃), which reactant is limiting?
H₂ (hydrogen).
Why is percent yield usually less than 100%?
Due to side reactions, loss of product, or incomplete reactions.
What is the molar mass of NaCl?
58.44 g/mol.
If 5g of Mg reacts with 10g of O₂ to form MgO, how do you determine the limiting reactant?
Convert grams to moles, then compare the mole ratio from the balanced equation.
If 3 moles of Na react with excess Cl₂ to produce 3 moles of NaCl, what is the percent yield if only 2.5 moles of NaCl are obtained?
83.3%