2023 TMJC H2 Chem Prelim P3 (QP)

2023 H2 Chem Prelim P3 (QP) Section A Answer all the questions in this section. 1 The Group 17 elements and its halides can react with many transition metals. (a) (i) Use the Data Booklet to describe the relative reactivity of the Group 17 elements as oxidising agents and relate this reactivity to relevant E⦵ values. [2] (ii) The following reagents are contained in three bottles labelled A, B and C. NaBr(aq) Cl2(aq) I2(aq) Table 1.1 shows the results of tests that were carried out using the reagents in the bottles. In each test, equal volumes of the reagents were mixed and the resultant colour of the solution was recorded. Table 1.1 test reagents mixed colour of resultant solution 1 A and B brown 2 C and B orange 3 A and C brown State the identity of the reagent in bottle A and write equations for any reactions that occur. [2] ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………...

2 2023 H2 Chem Prelim P3 (QP) Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Chemistry (b) Cobalt forms many complexes with ligands such as H 2O, NH 3 and Cl−. The most common oxidation states of cobalt are +2 and +3. Table 1.2 gives information about two octahedral cobalt(III) complexes D and E. Table 1.2 complex colour of aqueous ion D [CoCl2(NH3)4]+ violet E [Co(NH3)6]3+ yellow (i) Define the term complex. [1] (ii) The five d orbitals in a gas-phase transition metal ion are degenerate, but are split into two levels when the ion is in an octahedral complex. Explain why the d orbitals are split into two levels in an octahedral complex, including which of the d orbitals are in each level. [2] (iii) Draw the shapes of the d orbitals that occupy the higher energy level. [2] (iv) The colour of the complexes is due to the absorption of light at specific wavelengths. The colour observed is the complement of the colour absorbed. Suggest why the two complexes D and E have different colours. [1] ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... …………………………………………………………………………………………….