VJC Prelim P2

 VJC 2015 9647/02/PRELIM/15 [Turn over 2 1 Planning You are provided with 5 unlabelled bottles containing pure natural acids from the extracts of roasted coffee. Each bottle contains one of the following natural acids:  lactic acid,  maleic acid,  oxalacetic acid,  pyruvic acid,  quinic acid, All the acids above are soluble in water. You are also provided with any other common laboratory reagents and apparatus. (a) All natural acids contain one or more carboxylic acid functional groups. Other than the carboxylic acid functional grou p, what other functional groups are also present in these natural acids? lactic acid: ………………………………………………………..… maleic acid: ………………………………………………………..… oxalacetic acid: ………………………………………………………..… pyruvic acid: ………………………………………………………..… quinic acid: ………………………………………………………..… [2] (b) Two of these natural acids are colourless liquids and the rest are white crystalline solids. Using relevant chemical knowledge, identify the two liquids. Explain your choices. The two liquids are ………………………………….……………………………..… Explanation: ……………………………………………………..…………………….. ……………………………………………………………………….………………..… ……………………………………………………………………….………………..… [2] OH CO2H HO HO HO CH3COCO2H HO2CCOCH2CO2H CH3CH(OH)CO2H HO2CCH=CHCO2H

 VJC 2015 9647/02/PRELIM/15 [Turn over 3 (c) Suggest a reagent that could be used to carry out a test -tube ex periment to distinguish the two liquids. Reagent: ………………………………….……………………………..… Describe what would be observed for each compound in the experiment. Observation: ………………………………….……………………….……………..… …………………………………………………………………………………………… [2] (d) Outline a logical sequen ce of chemical tests that would enable you to identify the remaining 3 solids. You should aim for a minimum number of reactions. Your plan should include  a positive test to confirm the identity of each compound;  detailed procedure (including quantities of chemicals and conditions used);  expected observations for each compound in each test. [2]

 VJC 2015 9647/02/PRELIM/15 [Turn over 4 (e) How would you ensure the reliability of the test result for quinic acid? ……………………………………………………………………….………………..… ……………………………………………………………………….………………..… ……………………………………………………………………….………………..… [1] (f) Suggest a safety measure that you would consider in carrying out your plan. (g) ……………………………………………………………………….………………..… ……………………………………………………………………….………………..… ……………………………………………………………………….………………..… [1] Draw a set -up of the apparatus for the synthesis of pyruvic acid from lactic acid. State the required reagents and conditions. Reagents and conditions: ………………………………….…..…………………..… Diagram of the set-up: [2] [Total: 12]

 VJC 2015 9647/02/PRELIM/15 [Turn over 5 2 Use of the Data Booklet is required for this question