Stoichiometry exam problem clinic
≈ 48 minStoichiometry exam problem clinic
Stoichiometry is an argument from conservation and ratio, not a collection of disconnected formulas. Start with a balanced equation because it preserves atoms and gives the mole relationship. Identify the target quantity, convert the known amount to moles, use the coefficient ratio, then convert to the required unit. For limiting-reagent questions, repeat the comparison for each reactant before choosing a product yield. For concentration or gas questions, include the conditions and volume units. Examiners can award method marks when the pathway is visible, so write the equation, substitutions and units even if you can do mental arithmetic.
Work it through
For N₂ + 3H₂ → 2NH₃, if 2.0 mol H₂ reacts with enough nitrogen, n(NH₃) = 2.0 × 2/3 = 1.33 mol. The 3:2 coefficient ratio is applied to moles, not grams. If the question had given hydrogen mass, calculate moles first using H₂ molar mass. Round only at the end and check that producing fewer moles of NH₃ than H₂ is consistent with the ratio.
Mastery target
Complete an exam-style stoichiometry calculation with a balanced equation, mole conversion, coefficient ratio, units, limiting-reagent check where needed and a reasonableness statement.
For N₂ + 3H₂ → 2NH₃, what mole ratio H₂:NH₃ should be used?
Name the key chemistry term from Stoichiometry exam problem clinic that best fits the explanation and visual model.
For N₂ + 3H₂ → 2NH₃, how many moles of NH₃ form from 2.0 mol H₂ when N₂ is in excess? Give the numerical value to two decimal places.
Which statement corrects a common misunderstanding in Stoichiometry exam problem clinic?