| Date | May 2017 | Marks available | 2 | Reference code | 17M.3.sl.TZ1.4 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | State and explain | Question number | 4 | 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
State and explain how the graph would differ if 1 mol\(\,\)dm−3 sulfuric acid had been used instead of 1 mol\(\,\)dm−3 hydrochloric acid.
Markscheme
graph would peak/maximum at 17.5 cm3
OR
smaller volume of acid «needed to reach equivalence»
sulfuric acid is dibasic/diprotic
higher temperature would be reached
Accept “gradient/slope «of graph» is greater/steeper” for M1.
Accept “one mole of sulfuric acid neutralizes two moles of NaOH” for M2.
[2 marks]
