IJC H2 CHEM P3 Students Copy

INNOVA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION in preparation for General Certificate of Education Advanced Level Higher 2 CHEMISTRY Paper 3 Free Response Candidates answer on separate paper. Additional Materials: Writing Papers Data Booklet C o v e r P a g e 9647/03 26 August 2016 2 hours READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer any four questions. Begin each question on a fresh sheet of paper. You are advised to show all working in calculations. You are reminded of the need for good English and clear presentation in your answers. You are reminded of the need for good handwriting. Your final answers should be in 3 significant figures. At the end of the examination, fasten all your work securely together. The number of marks is given in the brackets [ ] at the end of each question or part question. This document consists of 12 printed pages. Innova Junior College [Turn over

2  IJC 2016 Prelim/9647/03 [Turn over Answer any four questions. 1 Data concerning the elements of group II of the Periodic Table, at 298K, are given in the table. Further data may be found in the Data Booklet. M refers to elements of group II. 1st and 2nd IE of M / kJ mol-1 ∆Hatom of M / kJ mol-1 ∆Hhydration of M2+ / kJ mol-1 Eө/ V Ca 1740 178 –1650 –2.87 Sr 1608 164 –1480 –2.89 (a) The electrode reduction potential Eө of Group II elements gives an indication of the ease with which the following reaction occurs: M(s) M 2+(aq) + 2e Reaction 1 The enthalpy change of reaction 1 can be related to the following factors:  first and second ionisation energy of the element  enthalpy change of atomisation and  enthalpy change of hydration of its gaseous ion.  (i) Construct an energy cycle relating the factors above, and use the values given above to calculate the enthalpy change of Reaction 1 for calcium. [3] (ii) By quoting appropriate data from Data Booklet, explain the difference in enthalpy change of hydration of calcium and strontium ions. [2] (b) Calcium oxide is the key ingredient for the process of making cement. When calcium is burned in oxygen, calcium oxide is produced. When 1.50 g calcium is burned in air, a mixture of ionic solids calcium oxide and red brown solid is formed. The red brown solid has the following composition by mass: Ca, 81.1%; N,18.9%. Adding water to the red brown solid produces calcium hydroxide and 19.2 cm 3 of ammonia gas at room temperature and pressure. (i) Calculate the formula of the red brown solid. [1] (ii) Write an equation for the reaction between red brown solid with water. [1] (iii) Write equations for the reactions of calcium with air and use them to calculate the mass of CaO formed when 1.5 g of calcium is burnt in air. [3] (c) Calcium oxide is normally made by heating ca lcium carbonate to a temperature above 825 oC. A gas which turns lime water chalky is produced in the process. (i) Write an equation for the decomposition of CaCO3. [1] (ii) Explain why barium carbonate decomposes at a higher temperature than calcium carbonate. [2]

3  IJC 2016 Prelim/9647/03 [Turn over (d) Methylcyclohexene reacts with hydrogen bromide to form alkyl bromides. + HBr C7 H13 Br met hylcycl ohexene (i) The above reaction could produce two isomers with molecular formula C 7H13Br. However, when the reaction is carried out, mainly one product is formed. Give the structural formula of the major product, explaining your answer. [2] (ii) Describe the mechanism of the reaction between hydrogen bromide and methylcyclohexene, C 6H9CH3, showing curly arrows, charges, dipoles and any relevant lone pairs. [3] (iii) Unsymmetrical dihalides reacts with alkene in a similar way as hydrogen halides. Predict the structure of the product when IBr reacts with methylcyclohexene, and explain your answer by considering the polarity within the molecule IBr. [2] [Total: 20]

4  IJC 2016 Prelim/9647/03 [Turn over 2 Alcohols and carboxylic acids have many scientific, medical and industrial uses worldwide. (a) Methanol is made from the following gaseous reaction. CO(g) + 2H2(g) ⇌ CH3OH(g) A 1:2 mixture of CO and H2 was pumped into a sealed reactor at 6 atm and then heated to 227 oC and maintained at this temperature for some time. When equilibrium was reached, the partial pressure of CH3OH was found to be 1.6 atm. (i) Write an expression for Kp for the reaction. Hence, determine the value of Kp stating its units. [3] (ii) Suggest the effect on the position of equilibrium and value of K p when methanol is removed from the reaction vessel. Explain your answer. [2] (b) Grignard reagent, RMgX, is an important reagent in organic synthesis. Grignard reagents are prepared by the addition of activated magnesium on an alkyl halide or aryl halide in non-polar solvents such as ether in anhydrous conditions. X + Mg MgX X = Cl or BrCH2R CH2R +- An example of a Grignard reagent reacting with a ketone to form an alcohol via a two stage process is given below: (i) Suggest the type of reaction occurred between the Grignard reagent and the carbonyl compound in Stage 1 and 2. [2] (ii) Suggest the structural formula of the final organic product formed when CH2MgBr is reacted with propanone, CH 3COCH3, in a similar two- step process. [1] (iii) Deduce the structures of a suitable Grignard reagent, RMgBr, and a suitable carbonyl compound, R’R’’CO, to synthesize the following alcohol, (CH 3)2CHCH2CH(OH)CH2CH2CH3. [2]

5  IJC 2016 Prelim/9647/03 [Turn over (iv) The Grignard reagent CH3CH2CH2MgBr can be readily converted into a carboxylic acid by using carbon dioxide. Suggest the structural formula of the organic product formed. [1] (v) The product formed by using Grignard reagent in (b) (iii) does not rotate the plane polarised light. Explain your reasoning. [2]