| Date | May 2017 | Marks available | 1 | Reference code | 17M.3.sl.TZ1.1 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Calculate | Question number | 1 | Adapted from | N/A |
Question
A class was determining the concentration of aqueous sodium hydroxide by titrating it with hydrochloric acid, whilst monitoring the pH of the solution. The sodium hydroxide solution was added into a glass beaker from a measuring cylinder and the hydrochloric acid added using a burette. One group of students accidentally used a temperature probe rather than a pH probe. Their results are given below.
Volume of aqueous NaOH = 25.0 ± 0.5 cm3
Concentration of HCl = 1.00 ± 0.01 mol dm−3
Calculate the percentage uncertainty of the volume of the aqueous sodium hydroxide.
Suggest how the precision of this measurement could be improved.
Markscheme
«\(\frac{{0.5}}{{25.0}} \times 100\)» = 2 «%»
[1 mark]
pipette/pipet «rather than a measuring cylinder»
Accept “using a burette/buret”.
Accept “using a volumetric/measuring flask”.
Do not accept “use of a more precise measuring cylinder”.
[1 mark]
