Copy of 2024 CGS Chemistry Prelim P3 Mark Scheme

CRESCENT GIRLS’ SCHOOL SECONDARY FOUR PRELIMINARY EXAMINATION MARK SCHEME 6092/03 CHEMISTRY 14 AUGUST 2024 PAPER 3 Practical 1 hour 50 minutes Shift Laboratory This document consists of 11 printed papers. For Examiner’s Use Q1 /17 Q2 /15 Q3 /8 Total /40 Class: Register No: Name: READ THESE INSTRUCTIONS FIRST Write your name, register number and class in the spaces provided 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 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 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.

2 CRESCENT/PRELIM/P3 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 1 You are to determine the enthalpy change of neutralisation of sodium hydroxide by an acid and the concentration of hydrogen ions in the acid. These can be found by measuring the temperature change when solutions of the acid and alkali are mixed. Read all the instructions below carefully before starting the experiments in Question 1. Instructions You are going to carry out seven experiments. P is 1.50 mol/dm3 sodium hydroxide, NaOH. Q is an aqueous solution of a strong acid. (a) Experiment 1 Place a Styrofoam cup into a 250 cm3 glass beaker. Put P into a burette and measure 40.00 cm 3 of P into the Styrofoam cup. Measure the temperature of P and record the value in the table. Use a measuring cylinder to measure 10.0 cm3 of Q. Pour this volume of Q into the Styrofoam cup containing P. Stir gently, using the thermometer, and measure the highest temperature reached. Record this temperature in the table. Empty the Styrofoam cup and rinse it with deionised water. Experiments 2 to 7 Repeat Experiment 1 but use different volumes of P and Q fo