Quantitative chemistry

The topics covered in this Starter for ten are: the mole; moles and mass; mass and concentration; concentration and dilution; moles summary; the ideal gas equation; molar gas volume; empirical and molecular formula; percentage yield and atom economy; and titration calculations.

Example questions

Work out the answers to the following simple calculations (1 t = 1 tonne = 1,000 kg);

1. No. of moles in 10.0 g of O₂ + the mass in g of 2.41 moles of H₂O =
2. Mass in g of 0.2 moles of K₂CO₃ + mass in g of 0.5 moles of MgCO₃ =
3. No. of moles in 12.4 t of NaNO₃ ÷ no. of moles in 12.4 t of NaCl =
4. No. of moles in 25.9 g of sodium – no. of moles in 25.9 g of sodium chloride =
5. ? × molar mass of in g mol^-1 of calcium carbonate = no. of moles in 4.2 kg of SiCl₄

Calculate the answers to the calculations below and place them (to the correct no. of sig. fig.) in the appropriate square. The arrows indicate the direction the numbers must follow. For the 10^th mark complete the remainder of the Sudoku grid. 

WARNING Take care with your significant figures and RAMs in order to avoid the wrong digit in the wrong square! (Relative atomic masses, H 1.0; O 16.0; Na 23.0; S 32.1; Cl 35.5; Fe 55.8; Cu 63.5)

• The concentration of a solution of 265 moles of NaOH dissolved in 1 dm³ of water (3 sig. fig.)
• The volume of water in dm³ needed to dilute 176 moles of HCl to make a 1 mol dm^-3 solution (3 sig. fig.)
• The mass of H₂SO₄ that should be dissolved in 1 dm³ of water to make a solution of concentration 0.72 mol dm^-3 (2 sig. fig.)
• The volume of water in cm³ that must be added to 0.56 g of anhydrous CuSO₄ to produce a 0.1 mol dm^-3 solution (2 sig. fig.)
• The number of moles of ammonia that must be dissolved in 2,696 dm³ of water to produce 2.0 mol dm^-3 ammonia solution (4 sig. fig.)
• The concentration in mol dm^-3 of an accurate solution of concentration 16.48537 mol cm^-3 (5 sig. fig.)
• The mass of FeSO₄.7H₂O that must be dissolved in 1,582 cm³ of water to form a solution of concentration 2.0 mol dm^-3 (to 3 sig. fig.)
• The volume in dm³ of water that 10 moles of NaCl must be dissolved in to produce a 0.0155 mol dm^-3 solution of brine (3 sig. fig.)
• The concentration in mol dm^-3 of a solution of NaOH with a concentration of 18,480 kg m^-3 (3 sig. fig.)

Notes

The full document, including questions and answers, are available from the ’Downloads’ section below. An editable version is also available.