NJC 2025 H2 Timed Practice 2 Paper (A and B)

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 fifteen 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 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 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 B 1.6 × 1.6 × 0.8 2.4 × 2.4 C 1.6 × 1.6 × 0.8 2.4 × 2.4 × 2 D 0.4 × 0.4 × 0.8 0.4 × 0.4

3 NJC SH2 Timed Practice 9729/A1/25 [Turn over 3 The concentration and pH of each solution, P, R and S are shown below. Solutions P, R and S could be either a monobasic acid or a monoacidic base. Which statements are correct? 1 1. R is a weak base. 2 1. P is a weak acid while S is a strong acid. 3 1. Mixing 100 cm3 of R and 100 cm3 of S produces a buffer solution. 2. 4 3. Mixing 500 cm3 of P and 500 cm3 of R produces a buffer solution. A 1 and 2 B 1 and 4 C 2 and 4 D 2 and 3 4 Equal volumes of 1.0  10–2 mol dm –3 aqueous BaSiF6 and 2.5  10–1 mol dm –3 aqueous CsBrO3 are mixed in a test-tube. The numerical values of the solubility products are: Ksp of Ba(BrO3)2 = 2.43  10–4 Ksp of Cs2SiF6 = 1.3  10–5 Which statement best describes what will be observed in the test tube? A No precipitation is observed. B Precipitation of Cs2SiF6 only. C Precipitation of Ba(BrO3)2 only. D Precipitation of both Cs2SiF6 and Ba(BrO3)2. P 1.0 mol dm–3 pH = 2.4 R 0.010 mol dm–3 pH = 12.0 S 0.001 mol dm–3 pH = 3.0

4 NJC SH2 Timed Practice 9729/A1/25 5 In the free radical substitution of 3 -methylpentane with chlorine, a mixture of products was obtained. How many constitutional isomers of mono-chlorinated products are theoretically possible? A 3 B 4 C 5 D 6 6 Nitrobenzene is a precursor to many reagents. It can be prepared by reacting benzene with concentrated HNO3 and concentrated H2SO4. What is the role of concentrated H2SO4? A To generate NO2− for the reaction B To act as a dehydrating agent C To direct the electrophile to a specific position on the benzene ring D To act as a catalyst 7 Equal amounts of compounds W, X, Y and Z are added separately to four test tubes containing equal concentrations of ethanolic silver nitrate solution in a heated water bath. No precipitate forms in two of the tubes. In the two other tubes, precipitates form at different rates. Which row is correct? Compounds which do not form a precipitate Colour of the precipitate which forms the fastest A W cream B W and X yellow C X and Z white D W and Y yellow

5 NJC SH2 Timed Practice 9729/A1/25 [Turn over 8 Which compound is less acidic than phenol? A B C D 9 Which reaction gives the best yield of the organic products? [(alc) indicates an alcoholic solution.] A OH + Br2 (g) r.t.p Br + HOBr(l) B heat in sealed tube NH2 (alc) + NH3 (alc) Br + HBr C Br (alc) + CH3CH2ONa (alc) heat + NaBr + CH3CH2OH D (l) + PCl5 (aq) r.t.p COCl + POCl3 + HCl CO2H

6 NJC SH2 Timed Practice 9729/A1/25 10 An iodoalkane and sodium, immersed in ether, react when heated under reflux to form an alkane according to the equation: 2RI + 2Na → R – R + 2NaI When iodoethane, CH3CH2I and 2-iodopropane, CH3CHICH3, are subjected to the reaction above, which alkane(s) will be formed? 1 2 CH3 CH2 CH CH3 CH3 3 A 1 and 2 only B 1 and 3 only C 2 and 3 D 1, 2 and 3 11 How many moles of H2 would react with one mole of the molecule below in the presence of Pt(s)? A 2 B 3 C 4 D 6 12 A compound Q was heated with aqueous sulfuric acid and potassium manganate(VII), and the resulting mixture was cooled. One of the final products gave a yellow precipitate with alkaline aqueous iodine. Which formula could Q represent? A CH3CO2CH3 B CH3CO2CH2CH3 C CH3CO2CH(CH3)CH3 D CH3CO2C(CH3)2CH3 CH3 CH CH3 CH CH3 CH3 CH3 CH2 CH2 CH3 C OH O C C H C O H H C N

7 NJC SH2 Timed Practice 9729/A1/25 [Turn over 13 Diazomethane (CH2N2) is a highly explosive yellow gas which is known to explode upon gentle impact or exposure to light. It is an efficient agent used in the preparation of methyl esters and the mechanism is shown below. R O O H Step I R O OCH3 Step II R O O CH2 N N N N R O O CH3 N N N NCH H H What types of reaction took place in Steps I and II? Step I Step II A nucleophilic substitution elimination B acid-base reaction elimination C nucleophilic substitution electrophilic addition D acid-base reaction nucleophilic substitution 14 Methylamine was heated in a seal ed tube with excess 1 -bromoethane for a prolonged period. Which is the major product? A CH5N B C3H9N C C5H13N D C7H18NBr

8 NJC SH2 Timed Practice 9729/A1/25 15 Compound R undergoes the following reactions. • It gives decolorises bromine water and gives white precipitate. • It does not give any visible reaction with Fehling’s solution. • It gives a silver mirror with Tollen’s reagent. • It does not give any visible reaction with sodium carbonate. What could compound R be? A OH C O CH3 NNO2 B CO2H CHO HO C OH NO2 CCHO D OH CH2CHO CCH3

NJC SH2 Timed Practice 9729/A2/25 [Turn over NATIONAL JUNIOR COLLEGE SH2 MID YEAR TIMED PRACTICE Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper A2 Structured Questions Candidates answer on Question Paper. Additional Materials: Data Booklet 9729/A2 30 May 2025 1 hour 30 min READ THE INSTRUCTIONS FIRST Write your subject class, registration number and name on all the work you hand in. Write in dark blue or black pen. You may use a