A sample of cosmetic jojoba-like wax is composed mainly of an unsaturated ester Y\text{Y}Y mixed with a small amount of an inert organic impurity. The unsaturated ester Y\text{Y}Y has the molecular formula C39H68O5\text{C}_{39}\text{H}_{68}\text{O}_5C39H68O5 (Mr=616M_r = 616Mr=616) and contains 3 carbon-carbon double bonds per molecule.
The amount of Y\text{Y}Y is determined using the following procedure:
A suitable target titre for the titration is 24.0 cm3 of 0.015 mol dm-3 Br2\text{Br}_2Br2.
Justify why a much smaller target titre would not be appropriate.
Calculate the amount, in moles, of bromine in this target titre.
Calculate a suitable mass of the cosmetic wax to transfer to the volumetric flask using your answer to Part 1 and the chemical structure of Y\text{Y}Y. Assume that the wax contains 75.0% of Y\text{Y}Y by mass. (If you were unable to calculate the amount of bromine in the target titre, you should assume it is 3.0 × 10-4 mol. This is not the correct amount.)
The wax solution is prepared using this method:
Suggest an extra step to ensure that the mass of wax in the solution is recorded accurately. Justify your suggestion.
State the reason for inverting the flask several times.
A sample of the cosmetic wax was dissolved in methanol and analysed using electrospray ionisation mass spectrometry. Each molecule gained a hydrogen ion (H+\text{H}^+H+) during ionisation. The spectrum showed a peak for an ion with m/z=281m/z = 281m/z=281 formed from an impurity in the wax. This ion was formed from a compound with the empirical formula C4H6O\text{C}_4\text{H}_6\text{O}C4H6O. Deduce the molecular formula of this compound, showing your working.