2025 YIJC [H2] Biology JC2 PE P4 ANS with Examiner Report

YISHUN INNOVA JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CG INDEX NO. H2 BIOLOGY 9744/04 22 Aug 2025 2 hours 30 minutes READ THESE INSTRUCTIONS FIRST Write your name and class in the spaces at the top of this page. Write in dark blue or black pen only. You may use a soft pencil for any diagrams or graphs. Do not use 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. The number of marks is given in brackets [ ] at the end of each question or part question. Shift Laboratory For Examiner’s Use 1 21 2 16 3 18 Total 55 This document consists of 18 printed pages and 2 blank pages.

2 @YIJC 9744/04/PE/2025 1 Plant extracts contain molecules which have many uses in industry and as medicines. It is important for scientists to be able to estimate the concentration of these molecules in plant extracts. You will estimate the concentration of molecule R in a sample of plant extract U. You are provided with the materials shown in Table 1.1. Table 1.1 labelled contents hazard volume / cm3 10R 10% solution of molecule R None 100 W Distilled water None 100 U Unknown concentration of molecular R in a plant extract None 40 A Sulfuric acid solution Harmful irritant 20 K Potassium manganate (VII) solution Irritant 20 If any of the solutions come in contact with your skin, wash off immediately under cold water. It is recommended that you wear suitable eye protection and wear gloves to protect your hands when using A and K.

3 @YIJC 9744/04/PE/2025 [Turn over (a) You will need to carry out a serial dilution of the 10% molecule R solution, 10R, to reduce the concentration by half between each successive dilution. You will need to prepare four concentrations of molecule R solution in addition to the 10% molecule R solution, 10R. After the serial dilution is completed, you will need to have 10 cm3 of each concentration available for use. (i) Complete Table 1.2 to show how you will prepare your serial dilution. Table 1.2 shows the first two beakers you will use to make your serial dilution. You will need to complete the table for three additional beakers. For each beaker, state: • the concentration of molecule R solution. • the concentration of molecule R solution transferred. • the volume of molecule R solution transferred. • the volume of distilled water, W, added. Table 1.2 Concentration of molecule R solution / % Concentration of molecule R solution transferred / % volume of molecule R solution transferred / cm3 volume of distilled water, W, added / cm3 10 - 0.0 0.0 5 10 10.0 10.0 2.5 5 10.0