Student can use balanced chemical equations to compute reactant and product masses, and identify the limiting reagent.
Explain how stoichiometric coefficients relate to moles and molecules.
The word stoichiometry comes from the Greek words stoicheion (element) and metron (measure). It deals with calculating the exact masses or volumes of reactants and products involved in a chemical reaction.
Visualizing stoichiometry with a balanced equation scale or mechanism diagram.
Always convert mass to moles before using the balanced equation's coefficients.
Problem 1.3: Amount of water from methane combustion.
Calculate the amount of water (g) produced by the combustion of 16 g of methane.
Problem 1.4: Moles of methane required to produce 22g CO2.
To find out how many moles of methane are required to produce of , we first write the balanced chemical equation: .
According to the equation, of is obtained from of .
Next, we convert the given mass of into moles using its molar mass. The number of moles of is calculated as .
Performing this calculation yields . Since the stoichiometric ratio of to is , producing this amount of carbon dioxide requires exactly of methane.
Define limiting reagent.
In real-world applications and laboratories, reactions are rarely carried out with the exact stoichiometric amounts of reactants dictated by the balanced equation.
Problem 1.5: Haber process limiting reagent.
50.0 kg of and 10.0 kg of are mixed to produce . Calculate the amount of formed. Identify the limiting reagent.
Exercise 1.23 conceptual limiting reagent questions.
Consider the reaction . Identify the limiting reagent for the following starting mixtures: (i) 300 atoms of A + 200 molecules of (ii) 2 mol A + 3 mol (iii) 5 mol A + 2.5 mol
List the starting amounts for each scenario.
State the molar or particle ratio from the balanced equation.
Compare what is available to what is required stoichiometrically for each case.
Explain which component runs out first based on your comparison.
State the limiting reagent for all three scenarios.
Optional: How can you quickly verify your logic makes sense?