2019 RVHS Prelim P4 QP

River Valley High School Pg 1 of 24 JC 2 H2 Chemistry 9729 Practical Examination 2019 RIVER VALLEY HIGH SCHOOL JC 2 PRELIM PRACTICAL EXAMINATION H2 CHEMISTRY 9729 26 AUGUST 2019 2 HOURS 30 MINUTES ATION II NAME CLASS 18J ( ) INDEX NO. INSTRUCTIONS TO CANDIDATES DO NOT OPEN THIS BOOKLET UNTIL YOU ARE TOLD TO DO SO. Read these notes carefully. Write your name, class and index number in the spaces at the top of this page. Give details of the practical shift and laboratory where appropriate, in the boxes provided. Write in dark blue or black pen. You may use a 2B pencil for any diagrams or graph. Do not use staples, paper clips, highlighters, glue or correction fluid. 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. Shift Laboratory For Examiner’s Use 3 s.f. Units Total 55 22 printed pages and 2 blank pages

River Valley High School Pg 2 of 24 JC 2 H2 Chemistry 9729 Practical Examination 2019 Answer all the questions in the spaces provided. 1 An experiment to investigate the behaviour of acids and bases in aqueous solution For Examiner’s Use For Examiner’s Use FA 1 is 1.00 mol dm–3 sodium hydrogencarbonate, NaHCO3 FA 2 is sodium hydroxide, NaOH, between 1.5 to 2.5 mol dm–3 FA 3 is 2.00 mol dm–3 sulfuric acid, H2SO4 According to the Arrhenius theory of acids and bases, an acid produces H+(aq) ions and a base produces OH–(aq) ions, in aqueous solution. Using the Arrhenius theory, an acid -base neutralisation reaction involves reacting together these two ions to produce water molecules. The equation for this neutralisation reaction is given below. H+(aq) + OH–(aq) H2O(l) ΔHneutralisation = –57.1 kJ mol–1 The reaction between H +(aq) and OH –(aq) involves bond formation and is exothermic. It is possible to make use of this fact to perform a thermometric titration. This task involves two different acid-base reactions. The first reaction is between sodium hydrogencarbonate, FA 1, and sodium hydroxide, FA 2. Reaction 1: NaHCO3(aq) + NaOH(aq) Na2CO3(aq) + H2O(l) ΔHreaction 1 The molar enthalpy change for Reaction 1, ΔHreaction 1, is the enthalpy change when 1.00 mol of NaHCO3 reacts completely with NaOH. Instead of using an indicator to determine the endpoint, you will perform a thermometric titration to determine the equivalence point of the reaction. The equivalence point is that point where H +(aq) from the acid and OH –(aq) from the base are present in equal molar amounts. The second reaction is between sodium hydrogencarbonate, FA 1, and sulfuric acid, FA 3. Reaction 2: NaHCO3(aq) + ½H2SO4(aq) ½Na2SO4(aq) + H2O(l) + CO2(g) ΔHreaction 2 The molar enthalpy change for Reaction 2, ΔHreaction 2, is the enthalpy change when 1.00 mol of NaHCO3 reacts completely with H2SO4. In your first experiment, you will perform a thermometric titration by adding portions of FA 2 progressively to a known volume of FA 1. You will continue adding FA 2 until the equivalence point is reached and passed. Throughout the experiment, you will note and record the temperature of the mixture after each addition.

River Valley High School Pg 3 of 24 JC 2 H2 Chemistry 9729 Practical Examination 2019 You will then analyse your results graphically in order to determine the • titration volume at the equivalence point, Vequivalence, • maximum temperature change, ΔTmaximum 1, • molar enthalpy change, ΔHreaction 1, for Reaction 1. In your second experiment, you will mix together a given volume of FA 1 with a suitable volume of FA 3. You will then determine the • maximum temperature change, ΔTmaximum 2, • molar enthalpy change, ΔHreaction 2, for Reaction 2. Reaction between FA 1 and FA 2 (a) (i) In this task you will need to record the maximum temperature of the reaction mixture when specified volumes of FA 2 have been added. It is important that the volume of FA 2 recorded is the total volume you have added up to that point when the temperature reading was made. Note: If you overshoot on an addition, record the actual total volume of FA 2 added up to that point. In an appropriate format in the space provided, record all values of temperature, T, to 0.1 °C, and each total volume of FA 2 added to 0.05 cm3. 1. Fill a burette with FA 2. 2. Place a Styrofoam cup inside a second Styrofoam cup which is held in a glass beaker to prevent it tipping over. 3. Using a pipette, transfer 25.0 cm 3 of FA 1 to the first Styrofoam cup. 4. Stir the FA 1 solution in the cup with the thermometer. Read and record its temperature. 5. From the burette, add 2.00 cm 3 of FA 2 to the cup and stir the mixture thoroughly. 6. Read and record the maximum temperature of the mixture, T, and the volume of FA 2 added. 7. Repeat points 5 and 6 until a total of 30.00 cm3 of FA 2 has been added. After each addition of FA 2 , record the maximum temperature of the mixture and the total volume of FA 2 added up to that point.

River Valley High School Pg 4 of 24 JC 2 H2 Chemistry 9729 Practical Examination 2019 Results For Examiner’s Use 1 2

River Valley High School Pg 5 of 24 JC 2 H2 Chemistry 9729 Practical Examination 2019 (a) (ii) On the grid below, plot a graph of temperature, T against volume of FA 2 added. 3 4 5 For Examiner’s Use (iii) Draw two smooth lines of best fit. Extrapolate these lines until they cross. Extrapolate these lines until they cross. 6 7 8 Supervisor Student Difference Supervisor Student Difference (iv) Determine from your graph, • the maximum temperature reached, Tmaximum, • the maximum temperature change, ΔTmaximum 1, • the volume, Vequivalence, of FA 2 needed to completely react with 25.0 cm3 of FA 1. Show on your graph how you obtained these values. Record these values in the spaces provided below. Maximum temperature reached, Tmaximum = ............................... Volume of FA 2 used, Vequivalence = ............................... Hence, calculate the maximum temperature change, ΔTmaximum 1 = ...............................

River Valley High School Pg 6 of 24 JC 2 H2 Chemistry 9729 Practical Examination 2019 Reaction between FA 1 and FA 3 For Examiner’s Use (b) The molar enthalpy change for Reaction 2 , ΔHreaction 2, is the enthalpy change when 1.00 mol of NaHCO3 reacts completely with H2SO4. In this task you will calculate a value for the molar enthalpy change, ΔHreaction 2 . To do this you will need to determine the maximum temperature change produced when measured volumes of FA 1 and FA 3 are mixed. After considering the concentrations of FA 1 and FA 3, you will select a suitable volume of FA 3 to add to 40 cm3 of FA 1. (i) Choose a suitable volume of FA 3, VFA 3, to be added to 40 cm3 of FA 1. Explain your answer. ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… 9 10 (ii) Identify the apparatus you intend to use to measure the volume of FA 1. Explain your choice. ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… 11 (iii) In an appropriate format in the space provided below, record all values of measured temperature for this experiment. 1. Label one Styrofoam cup, A. Label a second Styrofoam cup, B. 2. Place cup A inside a Styrofoam cup which is held in a glass beaker to prevent it from tipping over. 3. Transfer 40 cm3 of FA 1 into cup A. 4. Stir the FA 1 solution in cup with the thermometer. Read and record its temperature, TFA 1. This is