Copy of VS 2024 Sec 4 Chem Prelim Paper 3

Class Register Number Name 6092/03 CHEMISTRY 24/Prelim/6092/3 PAPER 3 WEDNESDAY 14 August 2024 1 hour 50 minutes VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA SCHOOL VICTORIA VICTORIA SCHOOL PRELIMINARY EXAMINATION SECONDARY FOUR READ THESE INSTRUCTIONS FIRST Write your name, class and index number on all the work you hand in. 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 HB pencil for any diagrams or graphs. Do not use staples, paper clips, 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. Qualitative analysis notes are printed on page 12. 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 question paper consists of 12 printed pages, including the cover page. [Turn Over For examiners’ use Question 1 / 19 Question 2 / 17 Question 3 / 4 Total / 40 Shift Laboratory

2 © Victoria School 24/4P/6092/3 [Turn Over 1 The reaction of aqueous solutions of strong acids and alkalis is exothermic. You are going to investigate the temperature rise when volumes of aqueous alkali and acid are mixed together. Read all the instructions carefully before starting the experiments in Question 1. Instructions You are going to carry out seven experiments. P is dilute sulfuric acid. Q is 1.23 mol/dm3 aqueous sodium hydroxide. (a) Experiment 1 Place a Styrofoam cup into a 250 cm 3 glass beaker. Put P into a burette and measure 40.00 cm3 of P into the Styrofoam cup. Measure the temperature of P and record the value in the table. Use a measuring cylinder to measure 10 cm3 of Q. Pour this volume of Q into the Styrofoam cup containing P . Stir, using the thermometer, and measure the highest temperature reached. Record this temperature in the table. Empty the Styrofoam cup and rinse it with water. Experiments 2 to 7 Repeat Experiment 1 but use the different volumes of P and Q for each experiment given in the table.

3 © Victoria School 24/4P/6092/3 [Turn Over Complete the table by calculating the temperature rise for each experiment. experiment volume of P /cm3 volume of Q /cm3 initial temperature of P /°C highest temperature of mixture /°C temperature rise /°C 1 40.00 10 2 35.00 15 3 30.00 20 4 25.00 25 5 20.00 30 6 15.00 35 7 10.00 40 [4]

4 © Victoria School 24/4P/6092/3 [Turn Over (b) Plot a graph of temperature rise against volume of Q on the grid below. Use these points to draw two intersecting straight lines of best fit. [4] (c) From your graph, read the volume of Q and the temperature rise where the two lines intersect. Show clearly on the graph how you obtained your answer. volume of Q = ……………...………… cm3 temperature rise = …………………….. °C [2]

5 © Victoria School 24/4P/6092/3 [Turn Over (d) (i) Write the chemical equation for the reaction between sodium hydroxide and sulfuric acid. ………………………………………………………………………………………….[1] (ii) Calculate the number of moles of P required to neutralise the volume of Q in (c). Number of moles of P = ……………...…………mol [1] (iii) Calculate the volume of P required to neutralise the volume of Q in (c). Volume of P = ……………...………… [1] (iv) Calculate the concentration of the sulfuric acid in P. Concentration of sulfuric acid in P = ……………...………… [2]

6 © Victoria School 24/4P/6092/3 [Turn Over (e) The energy change of the reaction in this experiment can be calculated by the expression shown. energy change (in J) = mass of solution (in g) x maximum temperature rise (in °C) x 4.2 Use this expression to calculate, in J, the energy change of the reaction. Leave your answer to 1 decimal place. Assume the density of the solution = 1.05 g/cm3 Energy change = ……………...………… [2] (f) The experiment was repeated using the same concentration of another acid, R. In this second experiment, the highest temperature obtained from the graph was approximately half that of the reaction with dilute sulfuric acid. Twice as much acid was also required to neutralise the aqueous sodium hydroxide. Two students made the following statements after studying the results. Student A: Acid R is a strong monobasic acid. Student B: Acid R is a weak dibasic acid. Comment on the two students’ statements. …………………………………………………………………………………………………….. …………………………………………………………………………………………………….. …………………………………………………………………………………………………….. ………………………………………………………………………………………………….[2] [Total: 19]

7 © Victoria School 24/4P/6092/3 [Turn Over 2 Read all the instructions carefully before starting the experiments in Question 2. (a) A is a 2.00 g sample of metal carbonate that is contaminated with an unknown salt, B. There is no need to weigh the sample of A. 1. Use a 50 cm3 measuring cylinder to add 50.0 cm3 of dilute nitric acid to the conical flask. 2. Weigh of the conical flask and acid and record the mass. 3. Carefully add all of sample A to the conical flask. Start the stopwatch at the same time. 4. Swirl the conical flask continuously for 2 minutes. 5. Reweigh the conical flask and its contents and record the mass. 6. Record all your results in an appropriate format. Results: [2]

8 © Victoria School 24/4P/6092/3 [Turn Over (b) You are provided with solutions X and Y, which are samples of A that have been reacted with excess dilute nitric acid and dilute hydrochloric acid respectively. Carry out the following tests and identify any gases evolved. R ecord your observations in the table. If no change is observed for a test, write ‘no observable changes’. The volumes given below are approximate and should be estimated rather than measured. test no. instructions observations 1 To 1 cm depth of X in a test tube, add aqueous ammonia slowly with shaking until no further change occurs. 2 To 2 cm depth of X in a boiling tube, add aqueous sodium hydroxide until no further change is observed. Warm the mixture gently. 3 To 1 cm depth of X in a test tube, add aqueous silver nitrate. 4 To 2 cm depth of Y in a boiling tube, add aqueous sodium hydroxide until no further change is observed. Add a piece of aluminum foil and warm the mixture gently.

9 © Victoria School 24/4P/6092/3 [Turn Over 5 To 1 cm depth of Y in a test tube, add aqueous barium nitrate. 6 To a 1 cm depth of Y, add aqueous potassium iodide until no further change is observed. Leave the mixture to stand. [6] (c) Conclusions (i) Tick (√) the most likely identity of the cation the metal carbonat