Quick answer: Reacting masses come from a balanced equation. This Chemistry 9-10 test on reacting masses has 9 questions worth 20 marks, to do in 45 minutes: balance and ratio, salt from sodium carbonate and phosphorus and oxygen. The mark scheme is on a separate page; free printable PDF.
This test has eight questions worth 20 marks in total. Show all working, give units, and use the relative atomic masses stated in each question. You may use a calculator.
Level: Chemistry grades 9-10 (GCSE · IGCSE · O Level · Class 9-10) · Curriculum: HS-PS1-7, GCSE C3
Question 1 Balance and ratio (2 marks)
Iron burns in chlorine: Fe + Cl₂ → FeCl₃.- Balance the equation. (1 mark)
- Calculate the moles of chlorine needed for 0.40 mol of iron. (1 mark)
Question 2 Salt from sodium carbonate (3 marks)
Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂. A technician uses 5.30 g of sodium carbonate and excess acid (Ar: Na = 23, C = 12, O = 16, Cl = 35.5).- Calculate the moles of Na₂CO₃. (1 mark)
- State the moles of NaCl formed. (1 mark)
- Calculate the mass of NaCl. (1 mark)
Question 3 Phosphorus and oxygen (3 marks)
4P + 5O₂ → 2P₂O₅. A student burns 0.20 mol of phosphorus in 0.30 mol of oxygen (Ar: P = 31, O = 16).- Identify the limiting reactant, showing your working. (2 marks)
- Calculate the mass of P₂O₅ formed. (1 mark)
Question 4 Yield and losses (2 marks)
A theoretical yield of 8.0 g gives 5.6 g of product.- Calculate the percentage yield. (1 mark)
- Explain one reason why the actual yield is lower than the theoretical yield. (1 mark)
Question 5 Concentration of a solution (2 marks)
Sodium hydroxide, 2.00 g, is dissolved and made up to 500 cm³ (Ar: Na = 23, O = 16, H = 1).- Calculate the concentration in mol/dm³. (1 mark)
- Calculate the moles of NaOH in a 25.0 cm³ sample. (1 mark)
Question 6 Mass concentration (2 marks)
Using the solution in the previous question:- Calculate its concentration in g/dm³. (1 mark)
- Explain why a 0.20 mol/dm³ solution is twice as concentrated as a 0.10 mol/dm³ solution. (1 mark)
Question 7 Reading a graph (2 marks)
Chidi adds magnesium to 50.0 cm³ of hydrochloric acid. The graph shows the mass of magnesium chloride formed.- State the mass of magnesium at which the acid runs out. (1 mark)
- Explain why the line is horizontal after this point. (1 mark)
Question 8 Explain the limiting reactant (2 marks)
A camping stove stops burning although there is still plenty of air.- State which reactant is limiting. (1 mark)
- Explain your answer. (1 mark)
Question 9 Silver nitrate solution (2 marks)
Chiamaka prepares 100 cm³ of 0.050 mol/dm³ silver nitrate (Ar: Ag = 108, N = 14, O = 16).- Calculate the moles of AgNO₃ needed. (1 mark)
- Calculate the mass of AgNO₃ to weigh out. (1 mark)
