Date | November 2017 | Marks available | 3 | Reference code | 17N.2.sl.TZ0.4 |
Level | SL | Paper | 2 | Time zone | TZ0 |
Command term | Determine | Question number | 4 | Adapted from | N/A |
Question
Menthol is an organic compound containing carbon, hydrogen and oxygen.
Complete combustion of 0.1595 g of menthol produces 0.4490 g of carbon dioxide and 0.1840 g of water. Determine the empirical formula of the compound showing your working.
0.150 g sample of menthol, when vaporized, had a volume of 0.0337 dm3 at 150 °C and 100.2 kPa. Calculate its molar mass showing your working.
Markscheme
carbon: «\(\frac{{0.4490\,{\text{g}}}}{{44.01\,{\text{g}}\,{\text{mo}}{{\text{l}}^{ - 1}}}}\)» = 0.01020 «mol» / 0.1225 «g»
OR
hydrogen: «\(\frac{{0.1840 \times 2}}{{18.02}}\)» = 0.02042 «mol» / 0.0206 «g»
oxygen: «0.1595 – (0.1225 + 0.0206)» = 0.0164 «g» / 0.001025 «mol»
empirical formula: C10H20O
Award [3] for correct final answer.
temperature = 423 K
OR
«M \( = \frac{{mRT}}{{pV}}\)
«M \( = \frac{{0.150\,{\text{g}} \times 8.31\,{\text{J}} {{\text{ K}}^{ - 1}}\,{\text{mol}}{}^{ - 1} \times 423\,{\text{K}}}}{{100.2\,{\text{kPa}} \times 0.0337\,{\text{d}}{{\text{m}}^3}}} = \)» 156 «g mol–1»
Award [1] for correct answer with no working shown.
Accept “pV = nRT AND n = \(\frac{m}{M}\)” for M1.