Copy of SCSS Prelim 2024 Chem P3 QP

SWISS COTTAGE SECONDARY SCHOOL SECONDARY FOUR PRELIMINARY EXAMINATION O Name Academic Class 4 A Form Class Register Number Form Class 4 S CHEMISTRY Paper 3 Practical Additional Materials: As listed in the Confidential Instructions 6092/03 Monday 9 September 2024 1 hour 50 minutes READ THESE INSTRUCTIONS FIRST Write your class, register number and name 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 an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue, correction fluid or highlighters. 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 in both parts separately. The number of marks is given in brackets [ ] at the end of each question or part question. Shift Laboratory For Examiner’s Use Question 1 Question 2 Question 3 Total This document consists of 11 printed pages and 1 blank page. [Turn over Home of Thoughtful Leaders: Serve with Honour, Lead with Humility

2 1 The reaction of magnesium and dilute hydrochloric acid is exothermic. You are going to investigate the temperature change when magnesium is added to dilute hydrochloric acid of different concentrations. Read all the instructions below carefully before starting the experiments in Question 1. Instructions You are going to carry out five experiments. P is 1.000 mol/dm3 hydrochloric acid. You are provided with five vials of magnesium. Each vial contains two pieces of magnesium ribbons each measuring 1 cm in length. (a) Experiment 1 Using a 10 cm3 measuring cylinder, pour 10 cm3 of P into a boiling tube. Measure the initial temperature of P in the boiling tube and record the value in the table. Transfer the magnesium ribbons from one of the vials to P in the boiling tube. Stir the mixture gently with the thermometer. Measure the highest temperature reached and record it in the table. Wash the thermometer and boiling tube with water. Experiments 2 to 5 Repeat Experiment 1, using different volumes of P and water given in the table. For example, in Experiment 2 measure 8 cm3 of P into the measuring cylinder and then add water to P until the total volume in the measuring cylinder is 10 cm3. Complete the table by calculating the change in temperature for each experiment. experiment volume of P / cm3 volume of water / cm3 initial temperature / C highest temperature / C change in temperature / C 1 10 0 2 8 2 3 6 4 4 4 6 5 2 8 [4]

3 (b) Use the results you have obtained in (a) to plot a graph of change in temperature against volume of P. Draw a line of best fit, taking into account all of your plotted points. [4]

4 (c) Describe and explain the trend shown by your graph in (b). ........................................................................................................................................... ........................................................................................................................................... .................................................................................................................................. [2] (d) Determine the expected change in temperature if the experiment was repeated with 0.0065 mol of dilute hydrochloric acid in the 10 cm3 solution. Show clearly on the graph how you obtained your answer. .................................................................................................................................. [2] (e) A student wanted to repeat the experiment using 10 cm3 of solution P and four pieces of magnesium ribbons of 1 cm length. He predicted that the temperature change would be twice that of Experiment 1. Explain if his prediction was correct. What was the assumption made in his prediction? ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... .................................................................................................................................. [2] (f) Give two observations, other than temperature change, made when magnesium reacts with dilute hydrochloric acid and explain each observation. observation 1 ..................................................................................................................... explanation ........................................................................................................................ observation 2 ..................................................................................................................... explanation ........................................................................................................................ [4]

5 (g) State one source of error, other than heat loss, in the results obtained in Experiments 1 to 5. Suggest one improvement you could make to the experiment to reduce this error. error ................................................................................................................................... ........................................................................................................................................... improvement ..................................................................................................................... ........................................................................................................................................... .................................................................................................................................. [2] [Total: 20]

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7 SWISS COTTAGE SECONDARY SCHOOL SECONDARY FOUR PRELIMINARY EXAMINATION O Name Academic Class 4 A Form Class Register Number Form Class 4 S CHEMISTRY Paper 3 Practical 6092/03 Monday 9 September 2024 2 Part 1 You are provided with a bleach solution Q, which contains an oxidising agent, the chlorate(I) ion. This ion liberates iodine from acidified aqueous potassium iodide. The iodine liberated can be titrated with aqueous sodium thiosulfate. From the titration results, the concentration of the bleach solution can be calculated. Read all the instructions below carefully before starting the experiment in Question 2. Instructions You are going to carry out a titration experiment. Q has been prepared by diluting a sample of 100 cm3 of commercial bleach to 1.00 dm3 by adding deionised water. R is 0.0500 mol/dm3 sodium thiosulfate. (a) (i) Put R into the burette. Pipette 25.0 cm3 of Q into a conical flask. Add about a test-tubeful of aqueous potassium iodide and about a test -tubeful of dilute sulfuric acid into this flask. The so