Copy of SKSS Chem Prelim Paper 3 + CI & MS

1 Name and Index Number: ( ) Class: SENG KANG SECONDARY SCHOOL 2024 PRELIMINARY EXAMINATION CHEMISTRY 6092/03 Secondary 4 Express 1 August 2024 Paper 3 Practical 1 hour 50 minutes Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions READ THESE INSTRUCTIONS FIRST Write your index number and name on all the work you hand in. Give the details of the practical shift and laboratory where appropriate, in the boxes provided. Write in dark blue or black pen. You may use a soft pencil for any diagrams or graphs. 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. Qualitative Analysis Notes are printed on page 10. 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. Shift Laboratory For Examiner’s use 1 / 18 2 / 18 3 / 4 Total / 40 % / Grade Parent’s / Guardian’s Signature: ………………….…………... This document consists of 10 printed pages. Do not turn over the page until you are told to do so.

2 1 A student suggests that the concentration of sulfuric acid can be determined by measuring the temperature of the solution as the acid is added in small amounts to a known volume of sodium hydroxide solution in a styrofoam cup. 2NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + 2H2O(l) The student proposes the following hypothesis. ‘As the acid is added to the alkali, the temperature rise will be directly proportional to the volume of acid added until the end -point of the reaction is reached. Upon further addition of acid there will be a reduction in the temperature of the solution in the cup as the acid added is not reacting and is at a lower temperature than the solution in the styrofoam cup.’ The following reagents are provided. A is approximately 0.75 mol/dm3 sulfuric acid, H2SO4. B is 2.00 mol/dm3 sodium hydroxide, NaOH. (a) Use the equation to estimate the volume of A that will neutralise 25.0 cm3 of B. volume of A = ………………………………. [1] (b) In this experiment, you will be adding A from a burette to 25.0 cm 3 of B in a styrofoam cup and measuring the temperature of the solution after each addition of a certain volume of A. In order to obtain precise information about the end -point of the reaction, you will need to decide on the: • volume of A to be added each time (