NJC 2025 H2 Timed Practice2 Paper A and B Answer booklet

1 NJC SH2 Timed Practice 9729/A1/25 [Turn over NATIONAL JUNIOR COLLEGE SH2 TIMED PRACTICE Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper A1 Multiple Choice Additional Materials: Optical Answer Sheet Data Booklet 9729/A1 30 May 2025 30 min READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Write your name, subject class and registration number on the Answer Sheet in the spaces provided unless this has been done for you. There are thirty questions on this paper. Answer all questions. For each question there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate Answer Sheet. Read the instructions on the Answer Sheet very carefully. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. Instructions on how to fill in the Optical Mark Sheet Shade the index number in a 5 digit format on the optical mark sheet: 2nd digit and the last 4 digits of the Registration Number. Example: Student Examples of Registration No. Shade: 2405648 45648 This document consists of 8 printed pages.

2 NJC SH2 Timed Practice 9729/A1/25 2025 SH2 H2 Chem Timed Practice Paper A1 Answer Key 1 D 6 D 11 C 2 C 7 D 12 C 3 C 8 D 13 D 4 B 9 C 14 D 5 B 10 D 15 C 1 The equilibrium percentage of Z varies according to varying pressures and temperatures as shown in the graph. Which row in the table shows the correct information about the equilibrium? equilibrium reaction sign of H for the forward reaction A Y(g) + X(g) 3Z(g) Positive B 4X(g) + Y(g) 2Z(g) Positive C Y(g) + X(g) 3Z(g) Negative D 4X(g) + Y(g) 2Z(g) Negative Ans: D Graph shows decreasing % of product Z with increasing temperature. As increasing temperature favours endothermic reaction, since less Z is formed, the backward reaction is endothermic, and the forward reaction is exothermic (C or D) Graph also shows increasing % of Z when pressure increases. As increasing pressure favours the side of the equation with fewer moles of gaseous particles, the RHS of the equation must have fewer gaseous moles than the LHS, so answer is D.

3 NJC SH2 Timed Practice 9729/A1/25 [Turn over 2 X decomposes on heating according to the following equation 2X(g) 2Y(g) + B(g) When 4 mol of X were put into a 2 dm3 container and heated, the equilibrium mixture contained 0.8 mol of B. What is the numerical value of the equilibrium constant, Kc? A 0.8 × 0.8 3.2