Skip to content
CIE Jun 2015 v3 Paper 3 Q2
Answers available below
Show answer
Question
1
2
3
![You are to determine the enthalpy change for the neutralisation reaction given below. HA(aq) + NaOH(aq)NaA(aq) + H2O(l) You will be using solutions of different concentrations from those in Question 1. FA 3 is 1.80 mol dm3 HA. FA 4 is aqueous sodium hydroxide, NaOH. (a) Method Read through the instructions carefully and prepare a table below for your results before starting any practical work.Support the plastic cup in the 250 cm3 beaker. Rinse and fill the burette with FA 3. Use the measuring cylinder to transfer 25 cm3 of FA 4 into the plastic cup. Place the thermometer in the plastic cup and record the temperature of the solution. Tilt the cup if necessary to ensure the thermometer bulb is fully immersed. Run 5.00 cm3 of FA 3 into the cup. Stir, and record the new temperature of the solution and the volume of FA 3 added. Run a second 5.00 cm3 of FA 3 into the cup. Stir and record the new temperature and the total volume of FA 3 added. Continue adding FA 3 in 5.00 cm3 portions. Stir and record each new temperature and total volume of FA 3 until a total of 45.00 cm3 has been added. Results II III IV [4] (b) Plot a graph of temperature (y-axis) against total volume of FA 3 added (x-axis) on the grid opposite. The temperature axis should allow you to include a point at least 2 C greater than the maximum temperature recorded.UCLES 2015 9701/33/M/J/15<br />
Draw the bestt smooth curve or straight line through the two sets of points, one for the increase in temperature of the mixture and the other for the cooling of the solution once the reaction is complete. Extrapolate the two lines and determine the maximum increase in temperature and the corresponding volume of FA 3 added for this increase in temperature. maximum temperature increase =C volume of FA 3 =cm3 [4] II III IVUCLES 2015 9701/33/M/J/15 [Turn over<br />
(c) Calculations Show your working and appropriate signi cantgures in thenal answer to each step of your calculations. (i) Calculate the number of moles of HA present in the volume of FA 3 recorded in (b). (ii) Using your answers to (b), calculate the heat energy produced when FA 3 neutralised 25 cm3 of sodium hydroxide. (Assume that 4.2 J of heat energy changes the temperature of 1.0 cm3 of solution by 1.0 C.) moles of HA =mol (iii) Calculate the enthalpy change of neutralisation, in kJ mol1, for the reaction below. HA(aq) + NaOH(aq)NaA(aq) + H2O(l) heat energy produced =J enthalpy change =kJ mol1 (sign) (value) [4] (d) The maximum error in a single thermometer reading is 0.5 C. Calculate the maximum percentage error in the increase in temperature recorded in (b). maximum percentage error =% [1] (e) When carrying out thermochemistry experiments in an A Level laboratory, the plastic cup is usually placed in a glass beaker. Give a reason for the use of the glass beaker.[1] (f) Apart from using a thermometer calibrated to a greater level of precision, suggest one improvement that could be made to the method carried out in (a).[1] [Total: 15]UCLES 2015 9701/33/M/J/15<br />](https://learnah.org/wp-content/uploads/2018/08/June_2015_v3_QP_-_Paper_3_CIE_Chemistry_A-level_2-0.jpg)
![Page 4 Question (a) Cambridge International AS/A LevelMay/June 2015 9701 33 Mark Scheme Syllabus Paper Indicative material Mark Total 1 1 [4] [4] I Table for 10 sets of results with unambiguous headings and correctly displayed units or table for 9 sets of results with separate line for initial T or table for 9 sets of results with column for initial T. II All volumes (apart from 0) recorded to 1 or 2 dp and all temperatures to 0.0 or 0.5 C. At least one thermometer reading should be recorded to 0.5 C. (Minimum 8 readings) Examiner to calculate Supervisors and candidates maximum T. Calculate the difference between the two values. III and IV awarded dependant on comparability between Supervisors and candidates T value. (b) I Linear scales chosen so that graph occupies more than half the available length for both axes (including extra 2 C for y-axis). and axes correctly labelled II All points recorded accurately plotted (withinsmall square and in the correct square, those on lines must be correctly centred). (If blobs shown then they must be correctly centred.) III Two lines of best fit drawnone for increasing temperature and one for decreasing temperature. (Allow a best fit (balanced points) straight line even if a smooth curve is more suitable for either or both.) IV Correct T using correct readings from graph (Tmax to within 0.2 C of examiner value) and correct V recorded from the intersection on graph (to within 0.5 cm3) (Tinitial may come from table or from graph plot or intercept on y-axis.) (c) (i) Correctly calculates 1.80 )( bV 1000 to minimum 2 sf (ii) Correctly calculates (25 + V(b)) x 4.2T to min 2sf (iii) Correct expression )( iic ))( ic 1000Cambridge International Examinations 2015<br />
Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A LevelMay/June 2015 9701 33 Answer given to 2 to 4 sf with negative sign Correctly calculates 1.0 100 )T( b to minimum 2 sf Safetyto prevent plastic cup tipping over / greater stability or (Reduce) heat lossair jacket / air trapped (owtte) Use burette / pipette for FA 4 / instead of measuring cylinder. or Use smaller volumes close to max T [4] [1] [1] [1] [15] (d) (e) (f) Qn 2Cambridge International Examinations 2015<br />](https://learnah.org/wp-content/uploads/2018/08/June_2015_v3_MS_-_Paper_3_CIE_Chemistry_A-level_2-0.jpg)
