R2.1 How much? The amount of chemical change
14 revision questions with answers for R2.1 How much? The amount of chemical change, marked SL. Read them here, or play the set as a class game on the projector. Free to host, and students join with a code.
Coefficients in a balanced equation give the ratio of reacting…?
- Amounts in molesRight answer
- Masses in grams
- Densities
- Volumes of solids
What this set covers
Quantities in chemical change: balancing equations, mole ratios, limiting and excess reactants, theoretical yield, percentage yield, atom economy, gas volume ratios and simple titration volumes.
- Common mix-up
- Students often mix up percentage yield and atom economy: yield compares actual with theoretical mass of product, while atom economy compares the desired product with all reactants in the equation.
- Revision tip
- For N₂ + 3H₂ → 2NH₃, work out the limiting reactant from the amounts, then calculate the theoretical yield from that reactant only.
All 14 questions and answers
Coefficients in a balanced equation give the ratio of reacting…?
Answer: Amounts in moles
Coefficient of Al when Al + O₂ → Al₂O₃ is balanced with whole numbers?
Answer: 4
Amount of H₂O from 0.50 mol of O₂ with excess H₂ (2H₂ + O₂ → 2H₂O)?
Answer: 1.0 mol
Maximum amount of NH₃ from 3.0 mol of H₂ with excess N₂ (N₂ + 3H₂ → 2NH₃)?
Answer: 2.0 mol
3 mol H₂ and 2 mol N₂ react (N₂ + 3H₂ → 2NH₃). Which runs out first?
Answer: Hydrogen
Reactant that is used up first and so sets the amount of product?
Answer: Limiting reactant
Reactant left over when a reaction stops?
Answer: Excess reactant
Maximum mass of product calculated from the balanced equation?
Answer: Theoretical yield
Mass of MgO from 0.10 mol of Mg (2Mg + O₂ → 2MgO; Mr of MgO = 40)?
Answer: 4.0 g
Percentage yield when 15 g is obtained and 20 g was expected?
Answer: 75%
Atom economy: desired product Mr = 60, total Mr of all reactants = 100?
Answer: 60%
Atom economy of a reaction whose only product is the desired one?
Answer: 100%
Volume of O₂ to burn 10 cm³ of CH₄ completely, at the same temperature and pressure?
Answer: 20 cm³
Volume of 0.10 mol dm⁻³ H₂SO₄ to neutralise 25.0 cm³ of 0.10 mol dm⁻³ NaOH?
Answer: 12.5 cm³
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.