Chemistry 9701/42 May June 2017 | Cambridge AS Level Past Papers With Mark Scheme

1. Thermal Stability of Group 2 Carbonates: Understanding the variation in thermal stability across Group 2 carbonates, explaining the trend with reference to ionic radii and lattice energies, and comparing the stability of sodium carbonate with magnesium carbonate.
2. Decomposition of Metal Carbonates and Hydrogencarbonates: Writing equations for the decomposition of potassium hydrogencarbonate and explaining why sodium hydrogencarbonate decomposes at a lower temperature.
3. Lattice Energy Calculations: Using thermodynamic data to calculate the lattice energy of potassium oxide and comparing it to sodium oxide, based on ionic sizes and bond energies.
4. Qualitative Analysis of Halides: Distinguishing between NaCl and NaI using AgNO3 and NH3, explaining the observations based on solubility and precipitation.
5. Rate of Reaction Studies: Investigating the rate of the nucleophilic substitution between 2-chlorobutane and sodium iodide in propanone, using conductivity measurements, and determining reaction orders with respect to the reactants.
6. Mechanisms of Organic Reactions: Understanding the SN2 mechanism for 1-bromobutane, drawing the reaction steps, and predicting stereoisomerism in the products.
7. NMR Spectroscopy and Isomer Identification: Interpreting the carbon-13 NMR spectra of organic compounds like CH3CH2CHClCH3, and identifying structural isomers based on their spectral data.
8. Organic Synthesis and Mechanism: Suggesting reagents for the synthesis of tyrosine from phenol, identifying the mechanisms, and predicting products of reactions such as the reaction of tyrosine with NaOH, HCl, and Br2.
9. Electrophoresis of Amino Acids and Peptides: Analyzing the results of electrophoresis on a mixture of phe-tyr dipeptide and its constituent amino acids, explaining how their migration relates to their charge and structure.