What mass of sodium hydroxide would need to be dissolved to make 100 cm^3 of a 0.5 mol dm^-3 solution? (3 marks)

Number of moles = (0.5 x 100)/1000 = 0.05 moles (1 mark)Molar mass, M, of NaOH = 23 + 16 + 1 = 40 (1 mark)Mass of NaOH needed = moles x M = 0.05 x 40 = 2g (1 mark)correct answer alone scores 3 markscorrect formula for working out moles or mass = 1 mark