PJC H1 Chemistry 2008 JC2 H1 Chemistry Prelim Paper 2

1 Name: Index No: CT Group: 07 PIONEER JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION 2008 CHEMISTRY 8872/02 Higher 1 Paper 2 16 September 2008 Additional Materials: Data Booklet 1 hour 30 minutes Writing papers READ THESE INSTRUCTIONS FIRST Write your name, CT Group and index number in the spaces at the top of this page. Write in dark blue or black pen. Answer all questions in Section A and any two questions in Section B. For Section A, write your answers in the spaces provided. For Section B, write your answers on the writing papers provided. If there is no answer to the question, a blank sheet of paper must still be submitted. You are advised to show all working in calculations. You may use a calculator. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, fasten all your work securely together. FOR EXAMINER’S USE Section A Section B 1 / 4 1 / 20 2 / 5 2 / 20 3 / 4 3 / 20 4 / 9 5 / 8 6 / 10 TOTAL This document consists of 13 printed pages. [Turn Over

2 Section A (40 marks) Answer all questions in the spaces provided. 1 (a) Complete the table below. [2] Number of Particle Electric charge Mass number Protons Electrons Neutrons X 0 16 16 Y 1- 81 36 Z 70 31 28 (b) Sketch on the diagram below how a beam of particle Y and a beam of particle Z would be affected by the electric field. [2] [Total: 4] 2 CO3 2- and SO3 2- ions are commonly found in many compounds. Although they have the similar formulae, they have different shapes. (a) What is the main feature of the electron pair repulsion model for accounting for shapes of molecules or ions? [1] _ + Source beams of particle Y and particle Z

3 (b) By means of dot-and-cross diagrams, predict the shapes of the ions. Account for the difference. [4] [Total:5] 3 (a) Describe the combustion of magnesium and phosphorus in excess oxygen, writing an equation for each reaction. [3] (b) It is found that magnesium burns less readily than calcium. Suggest a reason why this is so. [1] [Total: 4]

4 4 (a) Reaction of boron hydride with fluorine is a vigorous process and is used as rocket propellant. The reaction yi elds gaseous born fluoride, BF 3 as one of the products. An energy level diagram involving BF3 is shown below. Enthalpy / kJ mol-1 0 BF3(g) ΔHo at(B) B(s) + 3/2F2(g) B(g) + 3/2F2(g) B(g) + 3F(g) (i) Define the term standard enthalpy change of formation. [1] (ii) Using ∆H θ f(BF3), bond energy (B-F) and bond energy (F-F), label the enthalpy changes of the processes in volved on the energy level diagram above. [2] (iii) Hence, use the information given below and relevant data from the Data Booklet to calculate the bond energy of B-F bond. [2] Standard enthalpy change of formation of boron fluoride, ∆Hθ f(BF3) / kJ mol-1 -1137 Standard enthalpy change of atomisation of boron, ∆Hθ at(B) / kJ mol-1 +573

5 (b) A student used the apparatus below to determine the enthalpy change of combustion of propan-1-ol. It was found t hat 0.60 g of propan-1-ol was used to raise the temperature of 200 g of the water. The initia l temperature of the water was 21.0°C. The specific heat capacity of water is 4.18 J g-1 K-1. (i) Calculate the number of moles of propan-1-ol burnt. [1] (ii) Given that the enthalpy of combustion of propan-1-ol is -2021 kJ mol -1, calculate the final temperature of water at the end of the experiment. [2] (iii) The actual temperature of the water m easured at the end of experiment is 38.0°C. Give an explanation for the difference. [1] [Total: 9] thermometer copper can containing 200 g of water burner containing propan-1-ol

6 5 Consider the reaction scheme given below. OH CH2Br Step 1 A Step 2 OH CH2COOHStep 3 O CH2COOH CH3OH, concentrated H 2SO4 heat B (a) Give the structures of A and B in the boxes provided. [2] (b) Suggest reagents and conditions for [3] Step 1: _______________________________ Step 2: _______________________________ Step 3: _______________________________ (c) State the types of reactions occurring in [3] Step 1: _______________________________ Step 2: _______________________________ Step 3: _______________________________ [Total: 8]

7 6 The use of medicine in the treatment of illnesses was revolutionised in the 19th century and beyond due to rapid advancements in c hemistry, in terms of research work, laboratory techniques and equipment. An example of an important drug that has gained worl d-wide recognition for its medicinal properties is Ponstan. Ponstan capsules contain the active ingredient mefenamic acid, which is a type of medici ne called a non-steroida l anti-inflammatory drug (NSAID). NSAIDs are used to relieve pain and inflammation. The structure and some data of mefenamic acid are given below. C O OH NH CH3 CH3 mefenamic acid Formula : C 15H15NO2 Melting point : 230ºC Boiling point : 399ºC Density : 1.203 g cm -3 Protein binding : 90% Bioavailability : 90% pK a : 4.2 Solubility in water : 20 mg dm-3 Enthalpy of vaporisation : 68.5 kJ mol-1 Overdose : 740 mg kg-1 Route of administration : Oral Excretion : renal and fecal Adverse effects : drowsiness, dizziness, skin rashes, diarrhoea (a) To alleviate a case of migr aine, a patient was prescribed with a dose of the drug which includes two Ponstan capsules. Calculate the number of moles of mefenamic acid in the dose, given that each capsule contains 50 mg of mefenamic acid. [2]

8 (b) The patient took a dose of Ponstan at 8 am in the morning. The mefenamic acid took an hour to pass through the alimentary canal before being absorbed into the bloodstream. The graph below shows the variation in the amount of mefenamic acid in the patient’s blood with time. Use the graph to determine the half-life of mefenamic acid in the patient’s blood, showing the workings clearly. [2] (c) (i) Calculate the solubility, in mol dm-3, of mefenamic acid. [1] (ii) Account for the low solubility of mefenamic acid in water. [2] Amount of mefenamic acid /mol Time (hours)

9 (iii) To overcome the problem of low solubility, mefenamic acid is converted to sodium mefenamate. Suggest suit able reagent and condition f