2019 DHS Prelim H2 Chem P4 ANS

© DHS 2019 [Turn over Name: Index Number: Class: DUNMAN HIGH SCHOOL Preliminary Examinations 2019 Year 6 H2 CHEMISTRY 9729/04 Paper 4 Practical INSTRUCTIONS TO CANDIDATES 1 Write your name, index number and class on this cover page. 2 Give details of the practical shift and laboratory where appropriate, in the boxes provided. 3 Write in dark blue or black pen. 4 You may use an HB pencil for any diagrams or graphs. 5 Do not use staples, paper clips, glue or correction fluid. 6 Protective eye goggles and gloves must be worn at ALL TIMES. Answer ALL questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. The number of marks is given in brackets, [ ], at the end of each question or part question. Shift Laboratory For Examiner’s Use Question No. Marks 1 17 2 10 3 14 4 14 Total 55

2 © DHS 2019 9729/04 Answer all questions in the spaces provided. 1 Determination of acid concentration and enthalpy change of neutralisation using calorimetry When an acid is added into an alkali, an exothermic reaction takes place and the temperature of the mixture increases. Maximum heat is given out when stoichiometric amounts of H + and OH– are added together. FA 1 is an aqueous solution prepared by mixing equal volumes of y mol dm3 hydrochloric acid, HCl, and y mol dm3 sulfuric acid, H2SO4 FA 2 is 2.00 mol dm3 sodium hydroxide, NaOH In this question, you are to follow the neutralisation of known volumes of FA 2 , NaOH , by measuring the highest temperature obtained as different volumes of FA 1 are added. By measuring the maximum temperature rise for different mixtures of the two reagents, you are to determine the following.  the value of y, concentration of the acids present in FA 1  the enthalpy change of neutralisation, Hneut, for the reaction H+(aq) + OH(aq)  H2O(l) (a) Method 1 Fill the burette with FA 2. 2 Support the Styrofoam cup in a 250 cm3 glass beaker. 3 Run 20.00 cm3 FA 2 from the burette into the Styrofoam cup. Stir and measure the temperature of this FA 2. 4 Measure 20 cm3 FA 1 in a measuring cylinder. 5 Tip the FA 1 in the measuring cylinder into the FA 2 cup, stir and record the maximum temperature obtained in the reaction. 6 Rinse and carefully dry the Styrofoam cup. 7 Repeat steps 1 to 6 three more times, each time using 20.00 cm 3 of FA 2. Use 30.0 cm3, 40.0 cm3 and 50.0 cm3 of FA 1 respectively in these different experiments. Carry out two further experiments. Choose volumes of FA 1 which will allow you to investigate more precisely the volume of FA 1 that produces the highest temperature rise when added to 20.00 cm3 of FA 2. Record your results in an appropriate form