Set 16 Chemistry [Paper] 1

1 SECTION A: (46 MARKS) Answer all questions from this section. 1. (a) Complete the following equations for nuclear reactions . (i) 𝑆𝑖1427 𝐴𝑙1327+ …………………… (01 mark) (ii) 𝑈92236+𝑛01 2𝑛01+𝛾+ 𝑁𝑑+60147 ……… (01 marks) (b) When a radioactive isotope was left to stand, it decayed by 12.5% of its original value in 45 days . Calculate the half-life of the radioactive isotope. (2½ marks) …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………… ……………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… 2. (a) State three factors that can affect electron affinity . (1½ marks) …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………… ……………… (b) Write equation for the first electron affinity o f sulphur . (01 mark) …………………………………………………………………………………… (c) The first and second electron affinities of sulphur are −𝟐𝟎𝟎 and +𝟔𝟒𝟗 𝒌𝑱 𝒎𝒐𝒍−𝟏 respectively . Explain the difference in the electron affinities of sulphur. (04 mark s) …………………………………………………………………………………… ……………………………………… …………………………………... ……… …………………………………………………………………………………… …………………………………………………………………………………… 2 …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… 3. Polystyrene is formed by polymerization of phenylethene. (a) (i) Write the structural formula of polystyrene. (01 mark) …………………………………………………………………………………… ………………… ……………………………………………………….. ……… .. (ii) Name the type of polymerization involved in the formation of polystyrene. (½ mark) ………………… …………………………………………………………… (b) The osmotic pressu re of a solution containing 5.5g of polystyrene in 1 dm3 of benzene is 1.0 x 𝟏𝟎−𝟑atmospheres at 200C. (i) Calculate the relative molecular mass of polystyrene. (R = 0.082 atm dm3 𝐾−1𝑚𝑜𝑙−1) (02 marks) …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………… ……… …………………………………………………………………………… …………………………………………………………………………… (ii) Determine the number of monomers that formed the polystyrene. (1½ mark s) …………………………………………………………………………… ……………… …………………………………… ……………………… …………………………………………………………………………… 3 4. (a) The f igure below shows the energy diagram for the reaction between nitrogen monoxide and oxygen. (i) Identify K and L. K…………………………………………… (½ mark) L…………………………………………… (½ mark) (ii) State whether the reaction is endothermic or exothermic. (½ mark) …………………………………………………………………………..……… .. (iii) Give a reason for your answer in (a) (ii). (½ mark) …