Set 19 Chemistry [Paper] 1

Page | 1 PART A (46 MARKS) Attempt all questions in this section 1. (a) Complete the following nuclear transformation reactions. (3 marks) (i) 𝑃𝑢+𝑛→ 𝑆𝑒3486+ 𝑁𝑑60150±___ 𝑜1 94239 (ii) 𝐶𝑚 + 𝐻𝑒24→ ___________96242 (iii) 𝑈92235+𝑛 → 𝐿𝑎+3𝑛01+__________57148 𝑜1 (b) Francium isotope ( 𝐹𝑟87223) emits beta particles at a rate of 14.0 counts per second. The rate of emission decreased by 6.5 counts per second in 80 seconds. Calculate the half-life of the isotope. (2 ½ marks) 2. The thermochemical data for some process are given in the table below. Process ∆𝐻𝜎(𝐾𝐽𝑚𝑜𝑙−1) Rb(s) Rb(g) +78 Rb(g) Rb+(g)+e- +402 F2(g) 2F(g) +160 Rb+(g) + F (g) RbF (s) -762 F2(g) + 2Rb (s) 2RbF (s) -1104 Page | 2 (i) Use the above data to calculate the first electron affinity of fluorine. (3 marks) (ii) The first elect ron affinity of oxygen is -142KJmol-1 whereas the second electron affinity is +791 KJmol-1. Explain this observation. (2 marks) 3. Write equati ons to show how the following conversions can be effected. (i) (2 marks) (ii) CH 3CHO to CH 3CH=CH 2 (2 ½ marks) COCH 3 CHBrCH 3 to Page | 3 4. (a) Write equation for the reaction between phosphorus and aqueous sodium hydroxide solution. (1 ½ marks) (b) Compound G, contains 56.4% phosphorus the rest being oxygen. (i) Calculate the molecular formula of G (molar mass of G is 110) (3 ½ marks) (ii) Write equation for the reaction between G and water. (1 ½ marks) Page | 4 5. (a) Define the term solvent extraction. (1 mark) (b) An aqueous solution contains 10g of hydroxybenzene per litre. When 100cm3 of this solution is shaken with 20cm3 of ether, the layer extracts 0.8g of hydroxybenzene. Calculate the mass of hydrobenzene extracted when 500cm3 of aqueous layer was shaken with 50cm3 …