Stoichiometry
15 review questions with answers for Stoichiometry. Read them here, or play the set as a class game on the projector. Free to host, and students join with a code.
Ratio of moles of H₂ to NH₃ in N₂ + 3H₂ → 2NH₃?
- 2 : 3
- 1 : 2
- 3 : 1
- 3 : 2Right answer
What this set covers
Using balanced equations to compare amounts of reactants and products. Mole ratios, reacting masses, gas volumes, limiting reactant, theoretical yield, percentage yield and atom economy all appear, with methane, hydrogen and magnesium as the examples.
- Common mix-up
- Students often mix up percentage yield and atom economy: yield compares the product you actually got with the amount expected, while atom economy compares the useful product's Mr with the total Mr of the reactants.
- Review tip
- For 2Mg + O₂ → 2MgO, write the three-step route from grams to moles, then mole ratio, then back to grams, and apply it to the 12 g example.
All 15 questions and answers
Ratio of moles of H₂ to NH₃ in N₂ + 3H₂ → 2NH₃?
Answer: 3 : 2
Moles of O₂ needed to burn 2 mol of CH₄ (CH₄ + 2O₂ → CO₂ + 2H₂O)?
Answer: 4 mol
Moles of CO₂ made from 3 mol of C₂H₆ (2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O)?
Answer: 6 mol
Moles of H₂O formed from 0.5 mol of CH₄ (CH₄ + 2O₂ → CO₂ + 2H₂O)?
Answer: 1 mol
Mass of MgO made from 12 g of Mg (2Mg + O₂ → 2MgO; Mg = 24, MgO = 40)?
Answer: 20 g
Mass of CaO from heating 50 g of CaCO₃ (CaCO₃ = 100, CaO = 56)?
Answer: 28 g
Mass of water formed when 4 g of H₂ burns (2H₂ + O₂ → 2H₂O; H₂ = 2, H₂O = 18)?
Answer: 36 g
Reactant that is used up first and limits how much product forms?
Answer: Limiting reactant
2 mol of H₂ and 2 mol of O₂ react (2H₂ + O₂ → 2H₂O). Which is in excess?
Answer: Oxygen
Volume of 0.5 mol of CO₂ at room temperature and pressure (24 dm³ mol⁻¹)?
Answer: 12 dm³
Volume of H₂ from 0.1 mol Mg with excess acid (Mg + 2HCl → MgCl₂ + H₂; 24 dm³ mol⁻¹)?
Answer: 2.4 dm³
Mass of product expected from the balanced equation if everything reacts?
Answer: Theoretical yield
Percentage yield when 8 g of product forms but 10 g was expected?
Answer: 80%
Percentage of the reactants' atoms that end up in the useful product?
Answer: Atom economy
Atom economy if the useful product's Mr is 46 and the reactants' total Mr is 92?
Answer: 50%
Play it as a class game
Play this set opens it in splycr, where you can host it for your class straight away. Hosting needs no account: put the room code on the projector, and students join from a phone with the code and their first name. Each question plays as multiple choice, and the three wrong options were written for that question.