Four esters, $$$\mathbf{A}, \mathbf{B}, \boldsymbol{C}$$$ and $$$\mathbf{D}$$$, with the molecular formula $$$\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{2}$$$ are shown in Fig. 7.1. A mixture of these esters, A, B, C and D, is analysed by gas-liquid chromatography. The chromatogram produced is shown in Fig. 7.2. The number above each peak represents the area under the peak. The area under each peak is proportional to the mass of the respective ester in the mixture. (i) State what is meant by retention time. ....................................................................................................................................... . ................................................................................................................................. (ii) Calculate the percentage by mass of ester $$$\mathbf{D}$$$ in the original mixture. percentage by mass of ester $$$\mathbf{D}=$$$ .......................... \%

Chemistry

IGCSE&ALevel

CAIE

Exam No：9701_s24_qp_43 Year：2024 Question No：7(b)

Answer:

22.2.1 analyse mass spectra in terms of m/e values and isotopic abundances (knowledge of the working of the mass spectrometer is not required)

22.2.2 calculate the relative atomic mass of an element given the relative abundances of its isotopes, or its mass spectrum

22.2.3 deduce the molecular mass of an organic molecule from the molecular ion peak in a mass spectrum

22.2.4 suggest the identity of molecules formed by simple fragmentation in a given mass spectrum

22.2.5 deduce the number of carbon atoms, n, in a compound using the M +1 peak and the formula

22.2.6 deduce the presence of bromine and chlorine atoms in a compound using the M +2 peak