CAIE A-Level Chemistry Mathematical, Structural and Data Skills

Propanoic acid, methanoic acid and ethanedioic acid are all weak acids.

Draw the displayed formula of ethanedioic acid.

Alanine, $\mathrm{H}_{2} \mathrm{NCH}\left(\mathrm{CH}_{3}\right) \mathrm{CO}_{2} \mathrm{H}$, and glutamic acid, $\mathrm{H}_{2} \mathrm{NCH}\left(\mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CO}_{2} \mathrm{H}\right) \mathrm{CO}_{2} \mathrm{H}$, are two naturally occurring amino acids.

$\mathrm{H}_{2} \mathrm{NCH}\left(\mathrm{CH}_{3}\right) \mathrm{CO}_{2} \mathrm{H}$ exists as two optical isomers.

Draw three-dimensional structures of these two optical isomers.

Calcium carbonate decomposes on heating.

Table 4.1 shows the values of the Gibbs free energy change, $\Delta G^{\ominus}$, for this reaction at various temperatures.

Assume the standard enthalpy change, $\Delta H^{\ominus}$, and the standard entropy change, $\Delta S^{\ominus}$, for this reaction remain constant over this temperature range.

Use the data in Table 4.1 to plot a graph of $\Delta G^{\ominus}$ against T on the grid.

Some syntheses use Diels-Alder reactions, which normally involve a diene and an alkene reacting together to form a cyclohexene.

Draw three curly arrows in Fig. 9.4 to complete the mechanism for the Diels-Alder reaction between buta-1,3-diene and ethene.