NJC 2024 H1 Chem Prelim P1 QP

NJC/H1 Chem Preliminary Examination/01/2024 [Turn over NATIONAL JUNIOR COLLEGE SH2 PRELIMINARY EXAMINATION Higher 1 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 1 Multiple Choice Additional Materials: Optical Answer Sheet Data Booklet 8873/01 19 September 2024 1 hour READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, highlighters, 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. 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: 2305648 35648 This document consists of 12 printed pages

2 NJC/H1 Chem Preliminary Examination/01/2024 1 Use of the Data Booklet is relevant to this question. A sample of 35.6 g of hydrated sodium carbonate contains 25.84% sodium ions by mass. When this sample is heated, anhydrous sodium carbonate and water vapour are formed. What is the mass lost? A 7.2 g B 10.6 g C 14.4 g D 21.2 g 2 Diamond is an allotrope of carbon. The mass of a diamond can be measured in carats. One carat is 0.200 g of carbon. Which expression gives the number of carats that contain 6.02 × 1023 carbon atoms? A 0.200 × 12.0 B 12.0 0.200 C 0.200 12.0 D 0.200 6.02 × 1023 × 12.0 3 One of the main chemicals in air bags in cars is the ionic compound sodium azide, NaN3. When the car is in a violent head -on impact, a sensor causes ignition of the sodium azide to form nitrogen gas explosively, rapidly filling the air bag. I 2NaN3 → 2Na + 3N2 Fine particles of potassium nitrate and silicon dioxide are also present to react with the metallic sodium. II 2KNO3 + 10 Na → 5Na2O + K2O + N2 III K2O + SiO2 → K2SiO3 IV Na2O + SiO2 → Na2SiO3 Which statement is not correct? A Equations III and IV represent acid-base reactions. B In reaction I, sodium ions are reduced. C In reaction II, both sodium atoms and potassium ions are oxidised. D In reaction II, potassium nitrate is an oxidising agent.

3 NJC/H1 Chem Preliminary Examination/01/2024 [Turn over 4 When iodine is oxidized by nitric acid, a white crystalline solid oxide can be isolated from the mixture. 1 mol of this iodine oxide reacts with 10 mol of acidified potassium iodide to give 6 mol of I2. What is the oxidation number of iodine in the oxide? A +1 B +5 C +6 D +10 5 Use of the Data Booklet is relevant to this question. Sodium and fluorine are both reactive elements. Which statements are correct? 1 One Na atom has two more protons than one F− ion. 2 One Na atom has two more neutrons than one F atom. 3 One Na+ ion has the same number of electrons as one F− ion. A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 1 only 6 Which pair of compounds meets the criteria below? • The first compound has a larger bond angle than the second compound. • The second compound is more polar than the first compound. A CO2, BCl3 B SF6, H2O C HCN, SO3 D CO2, NH3 7 Which statements about the structure of the AlCl3 molecule are correct? 1 The aluminium atom has an unfilled octet. 2 The molecule is planar in shape. 3 In the molten state, it consists of Al3+ and Cl− ions. A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 1 only

4 NJC/H1 Chem Preliminary Examination/01/2024 8 Consider the following four compounds. 1 (CH3)3CH 2 CH3CH2CH2CH3 3 CH3CH2CH2OH 4 CH3CH2Cl What is the order of increasing boiling point of the compounds? A 1 2 4 3 B 2 1 4 3 C 3 4 2 1 D 4 3 2 1 9 The diagram below represents the energy changes associated with NaHCO3 and H2SO4. ∆H / kJ mol─1 NaHCO3(s) + aq → NaHCO3(aq) + 15.0 2NaHCO3(s) + H2SO4(aq) → Na2SO4(aq) + 2H2O(l) + 2CO2(g) + 37.0 Determine the value of ∆H1. A + 7.0 kJ mol−1 B + 22.0 kJ mol−1 C + 37.0 kJ mol−1 D +52.0 kJ mol−1 ∆H1

5 NJC/H1 Chem Preliminary Examination/01/2024 [Turn over 10 In order to determine the enthalpy of neutralisation of a strong acid and a strong alkali, 25.0 cm3 of 2.00 mol dm−3 sodium hydroxide is added to 25.0 cm3 of 2.00 mol dm−3 hydrochloric acid. The increase in temperature is 12°C. In a second experiment, the same method is used, but 50.0 cm 3 of 2.00 mol dm −3 sodium hydroxide is added to 50.0 cm3 of 2.00 mol dm−3 hydrochloric acid. What is the increase in temperature in the second experiment? A 6°C B 12°C C 24°C D 48°C 11 What is meant by the term dynamic equilibrium? A An equilibrium that is constantly changing its position B An equilibrium where the forward and reverse reactions are taking place at different rate C An equilibrium where the forward and reverse reactions are taking place at the same rate D An equilibrium which has not yet settled to a constant state 12 X and Y react together to form Z in a reversible reaction. The equilibrium yield of Z at different conditions are shown in the following table. Conditions Equilibrium yield of Z High Temperature Decreased High Pressure Increased Which equation could represent this reaction? A X(g) + Y(g) ⇌ Z(g) ∆H = –100 kJ mol-1 B X(g) + Y(g) ⇌ Z(g) ∆H = +100 kJ mol-1 C X(s) + Y(g) ⇌ 2Z(g) ∆H = –100 kJ mol-1 D X(s) + Y(g) ⇌ 2Z(g) ∆H = +100 kJ mol-1

6 NJC/H1 Chem Preliminary Examination/01/2024 13 PCl5 decomposes as shown. PCl5(g) ⇌ PCl3(g) + Cl2(g) 1.0 mol of PCl5(g), 1.0 mol of PCl3(g) and 1.0 mol of Cl2(g) are placed in a container of volume 2 dm3 at 250 °C and allowed to reach equilibrium. At this temperature, the equilibrium mixture contains 1.8 mol of PCl3. What is the value of Kc at 250 oC? A 0.12 B 1.8 C 8.1 D 16.2 14 Ammonium carbonate is a crystalline solid. On gentle warming a reaction occurs, forming ammonia as one product. How are the carbonate ions behaving during this reaction? A Brønsted-Lowry acid B Brønsted-Lowry base C oxidising agent D reducing agent 15 The dissociation constant, Kw, for the ionisation of water, H 2O ⇌ H+ + OH –, at different temperatures is given below. Temperature / C Kw / mol2 dm-6 0 1.15 × 10–15 25 1.00 × 10–14 50 5.50 × 10–14 Which statement is correct? A Only at 25 C are [H+] and [OH–] equal. B The equilibrium lies furthest to the right at 0 C. C The forward reaction is exothermic. D The pH of water decreases with temperature.

7 NJC/H1 Chem Preliminary Examination/01/2024 [Turn over 16 The indicator bromophenol blue, HIn, changes colour from yellow to blue over a pH range of 3.0 to 4.6. Which statements are correct? 1 When bromophenol blue is added to water at 25 C, [HIn] < [In–]. 2 Bromophenol blue would be a suitable indicator for the titration of a strong base and a weak acid. 3 The In– ions are yellow. A 1,2 and 3 B 1 and 3 only C 1 only D 2 and 3 only 17 Which statement about catalysts is correct? A Catalysts alter the reaction pathway by increasing the activation energy. B Catalysts