TJC H1 CHEM P2 (A) QN

2015 TJC H1 Chemistry Preliminary Exam s CANDIDATE NAME CIVICS GROUP / CENTER NUMBER S INDEX NUMBER CHEMISTRY 8872/02 Paper 2 1 September 2015 2 hours Candidates answer section A on the Question Paper. Additional Materials: Answer Paper, Graph Paper Data Booklet READ THESE INSTRUCTIONS FIRST Write your Civics Group, centre number, index number and name on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all questions. Section B Answer two questions on separate answer paper. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 16 printed pages. For Examiner’s Use A1 / 10 A2 / 10 A3 / 10 A4 / 10 Section B / 40 Paper 1 / 30 Total PRELIMINARY EXAMINATIONS HIGHER 1

2 2015 TJC H1 Chemistry Preliminary Exam [Turn over For examiner’s use 1 (a) An acidified solution of KC lO2 oxidises Fe2+(aq) to Fe 3+(aq). When 0.150 g of KC lO2 reacted with 0.500 mol dm -3 Fe2+(aq) in the presence of H +(aq), 11.30 cm 3 of Fe 2+(aq) was needed for complete reaction. (i) Suggest the final oxidation state of chlorine after complete reaction. Show your workings clearly. (ii) State the full electronic configuration of Fe3+. [4]

3 2015 TJC H1 Chemistry Preliminary Exam [Turn over For examiner’s use (b) The research student was given the second ionisation energies of seven consecutive elements in the Periodic Table as shown below: (i) Define, with the aid of an equation, what is meant by second ionisation energy of element B. (ii) With reference to the graph above, deduce the Group of the Periodic Table to which B is likely to belong. Explain your answer. [4] Second ionisation energy /kJ mol-1 B C D E F G H       

4 2015 TJC H1 Chemistry Preliminary Exam [Turn over For examiner’s use (c) When the student passed a beam of protons through an electric field, it deflected 12° towards the negative plate. Under identical conditions, the student passed a beam of doubly charged particles J through the electric field. The angle of deflection was found to be 1.5° towards the positive plate. Identify the ion J. [2] [Total: 10]

5 2015 TJC H1 Chemistry Preliminary Exam [Turn over For examiner’s use 2 (a) Acid rain ha s harmful effects on aquatic animals , plants and infrastructure. It contains sulfuric acid formed from sulfur trioxide. Sulfur trioxide is produced upon atmospheric oxidation of sulfur dioxide from coal burning. (i) Write an equation for the formation of sulfuric acid from sulfur trioxide. Even before the existence of acid rain, unpolluted rain water was slightly acidic due to dissolved CO2. The solubility of pure carbon dioxide gas in water is 88 cm 3 per 100 cm3 of water under room conditions. (ii) Given that air contains 0.033% by volume of carbon dioxide, calculate the concentration in mol dm3 of carbon dioxide dissolved in unpolluted rain water. Dissolved carbon dioxide forms carbonic acid in water, causing the pH of unpolluted rain water to be 5.63. (iii) Calculate the [H+] in unpolluted rain water. Some fishes and shellfish die at low pH values. Lakes with limestone -rich soil can maintain a relatively stable pH even when acid rain falls due to the HCO 3 /CO3 2 buffer system. (iv) With aid of an equation, explain how lakes with limestone -rich soil maintain a relatively stable pH in presence of acid rain. [6]

6 2015 TJC H1 Chemistry Preliminary Exam [Turn over For examiner’s use (b) Oxides and halides of Period 3 elements have many applications. A farmer intends to add a magnesium -containing compound to his farmland to correct magnesium deficiency and raise soil pH. (i) Suggest whether the farmer should add magnesium oxide or magnesium chloride to his farmland. (ii) Explain your answer in (b)(i) by describing the reactions of the compound suggested with water and acid. Write equations where appropriate and s tate the pH of the solution formed when the compound is dissolved in water. [4] [Total: 10]

7 2015 TJC H1 Chemistry Preliminary Exam [Turn over For examiner’s use 3 (a) Levulinic acid is a keto -acid which is derived from degradation of cellulose and is a potential precursor to biofuels. (i) Arrange pentanoic acid, levulinic acid and pentan-1-ol in order of increasing pK a, explaining your answer. Levulinic acid

8 2015 TJC H1 Chemistry Preliminary Exam [Turn over For examiner’s use (ii) Carboxylic acids are often used as precursors in the synthesis of esters. Devise a 2-step synthesis to convert levulinic acid to the cyclic ester shown below. Suggest the reagent and condition s used in each step and the structural formula of the intermediate formed. [6] (b) Another ester, isopentyl acetate, is responsible for the smell associated with bananas. It is used as flavouring in a variety of processed foods such as cakes and sweets. isopentyl acetate (i) Draw the structure of the organic compounds formed when isopentyl acetate is heated with NaOH(aq). Isopentyl acetate

9 2015 TJC H1 Chemistry Preliminary Exam [Turn over For examiner’s use (ii) Isopentyl acetate is found to be only slightly soluble in water. In terms of structure and bonding, suggest an explanation for this. [4] [Total: 10]

10 2015 TJC H1 Chemistry Preliminary Exam [Turn over For examiner’s use 4 Citramalic acid can be obtained from citraconic acid. Citraconic acid is used as a fire retardant. The following reaction scheme shows some of the reactions of citraconic acid. citraconic acid citramalic acid Compound K Compound L (a) State the functional groups present in citramalic acid. [1] (b) State the reagents and conditions needed for Stages I and II. [3] Reagents and Conditions Stage I Stage II (c) State the type of reaction for Stage I and Stage II. Stage I : ……………………………………….. Stage II: ………………………………………… [2] (d) Draw the structures of the organic compounds K and L in the boxes in the scheme. [2]