1. 1.(a) 0.0120(b) 1.3(c) 0.100 2.moles of CaCl 2 = 1.23/111.1 = 0.01107 moles Ca 3 (PO 4 ) 2 = 1/3 × 0.01107 = 0.003690 mass Ca 3 (PO 4 ) 2 = 0.003690 × 310.3 = 1.15 g 3.moles H 2 O 2 = 3.60/34 = 0.1059 mol moles O 2 produced = 1/2 × 0.1059 = 0.05294 mol volume of O 2 (g) = 24 dm 3 mol −1 × 0.05294 mol = 1.27 dm 3 4.volume of Cl 2 needed = 4 × volume CH 4 = 4 × 25.0 cm 3 = 100 cm 3 5.(a) moles of S = mass/molar mass = 32 × 10 6 g/32 g mol −1 = 1 × 10 6 = moles of H 2 SO 4 mass of H 2 SO 4 = moles × molar mass = 1 × 10 6 × 98 = 98 × 10 6 g = 98 tonne % yield = (95/98) x 100 = 99% (b) The atom economy is 100% (the equation has only one substance on the right of the equation) 6.molar mass = (6 × 12) + 12 + (6 × 16) = 180 g mol −1 mass of carbon in 1 mol = 6 × 12 = 72 g % carbon = (72/180) × 100 = 40% © Hodder & Stoughton 2015 9 Calculations from chemical Answers to equationsTest yourself questions

2. 7.molar mass of NaHCO 3 = 84 g mol −1, so moles taken = mass/molar mass = 4.20/84 = 0.05 mol If equation 1: moles of Na 2 O = ½ × 0.5 = 0.025: mass = moles × molar mass = 0.025 × 62 = 1.56 g  22.65 g, so not equation 1. If equation 2: moles of Na 2 CO 3 = 0.025, so mass = 0.025 × 106 = 2.65 g, so equation 2 is correct. (If equation 3: moles of NaOH = 0.05, so mass = 0.05 × 40 = 2.0 g, so equation 3 is incorrect) 8.(a) moles = volume × concentration = 0.025 dm 3 × 0.104 mol dm −3 = 2.6 × 10 −3 mol (b) volume = moles/concentration = 0.0260 mol/0.0500 mol dm −3 = 0.52 dm 3 = 520 cm 3 9.moles of acid = concentration × volume = 0.512 mol dm −3 × 0.02375 dm 3 = 0.001216 mol moles of NaOH = 2 × 0.001216 = 0.002432 mol concentration of NaOH = moles/volume = 0.002432 mol/0.0250 dm 3 = 0.0973 mol dm −3 © Hodder & Stoughton 2015 9 Calculations from chemical Answers to equationsTest yourself questions

3. 10.Error in weighing = ± 2 × 0.01 = ± 0.02 g% error = (0.02/0.45) × 100 = 4.4% Error in pipette = ± 0.05 cm 3 % error = (0.05/10) × 100 = 0.5% Error in titre = ± 2 × 0.05 = ± 0.10 cm 3 % error = (0.10/12.25) × 100 = 0.82% (a) Lowest error is that using the pipette (b) Total error = 4.4 + 0.5 + 0.82 = 5.7% © Hodder & Stoughton 2015 9 Calculations from chemical Answers to equationsTest yourself questions