2021 NJC Prelim P1 Qns

1 8873/01 [Turn over NATIONAL JUNIOR COLLEGE SH 2 PRELIMINARY EXAMINATION Higher 1 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 1 Multiple Choice Additional Materials: Multiple Choice Answer Sheet Data Booklet 8873/01 Wednesday 15 September 2021 1 hour 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: 1st digit and the last 4 digits of the Registration Number. Example: Student Examples of Registration No. Shade: 2005648 25648 This document consists of 15 printed pages and 1 blank page.

2 8873/01 [Turn over 1 Which statement about 1 mol of a metal is always true? 1. It has the same number of atoms as 1 mol of hydrogen atoms. 2. It loses 1 mol of electrons. 3. It contains half the number of atoms as 2 mol of HCl(g). 4. It contains 1 3 the number of ions as 3 mol of Na2O(s). A 1 B 1 and 3 C 1, 2 and 3 D 1, 3 and 4 2 The actual values of the masses of three sub-atomic particles are shown in the table. proton neutron electron mass/kg 1.673  1027 1.675  1027 9.109  1031 Which nickel ion is predicted to have a mass of 1.038  1025 kg from these data? A 𝑁𝑖28 60 2+ B 𝑁𝑖28 62 2+ C 𝑁𝑖28 58 3+ D 𝑁𝑖28 64 3+ 3 The redox half-equations for the electrolysis of dilute sodium chloride solution are stated below. Oxidation half-equation: 2H2O → O2 + 4H+ + 4eˉ Reduction half-equation: 2H2O + 2eˉ → H2 + 2OHˉ Which row shows the correct volume of gases if 2.40 mol of electrons are involved in the redox reaction? Volume of H2 gas collected at r.t.p / dm3 Volume of O2 gas collected at r.t.p / dm3 A 28.8 14.4 B 28.8 28.8 C 14.4 7.2 D 14.4 28.8

3 8873/01 [Turn over 4 Use of the Data Booklet is relevant to this question. To identify a compound, the compound can be broken down into ions and passed through an electric field. In this electric field, the 4He nucleus is deflected +8o and used as a standard. An unknown ionic compound was broken down and passed through the same electric field. Two monocharged fragments were observed to have deflected +0.6o and −0.45o. What could be the ionic compound? A LiCl B LiBr C NaCl D NaBr 5 10 cm3 of propane, C3H8, was completely burnt in x cm3 of excess oxygen. After cooling to room temperature, the volume of the residual gas was 60 cm3. The residual gas was passed through aqueous sodium hydroxide and the volume reduced to y cm3. What are the values of x and y? x y A 50 30 B 60 30 C 70 20 D 80 30 6 Propyne, C3H4, has the following structure. Which option correctly describes the number of σ and π bonds present in a molecule of propyne? σ π A 2 2 B 2 6 C 1 3 D 6 2

4 8873/01 [Turn over 7 Which statement is true for all covalent bonds? A A covalent bond cannot be found in ionic compounds. B A covalent bond can be formed via head-on overlap of p orbitals. C A covalent bond can only be formed between two non-metal atoms. D A covalent bond is formed when each bonding atom contributes a valence electron. 8 Which conditions would result in the most significant intermolecular forces between gaseous oxygen molecules? pressure temperature A high low B High high C low high D low low 9 Which statements can be explained in terms of hydrogen bonding? 1 The apparent relative molecular mass of ethanoic acid in benzene is 120. 2 HF2‒ is formed when HF is dissolved in molten NaF. 3 The boiling point of propanoic acid is higher than ethanoic acid. 4 Ice is less dense than water. A 1, 2 and 3 B 2, 3 and 4 C 1, 2 and 4 D 1 and 4

5 8873/01 [Turn over 10 Which species is not planar? A BrF3 B ICl4 C PCl4+ D XeF4 11 Which statements are correct for all systems at dynamic equilibrium? 1 It is a closed system. 2 The rate of both forward and backward reactions is the same. 3 The concentration of reactants is equal to the concentration of products. A 1 and 2 only B 1 and 3 only C 2 and 3 only D 2 only

6 8873/01 [Turn over 12 Nitrosyl chloride, NOCl, is a yellow gas that can be formed between nitryl chloride, NO 2Cl, and nitric oxide, NO, in the following reaction. NO2Cl(g) + NO(g) ⇌ NOCl(g) + NO2(g) ∆H < 0 NO2Cl and NO were initially allowed to react in a closed vessel at 800 K and equilibrium was established. The graph below shows how the concentration of NO2Cl varied with time. What could be the changes made to the system at t1, t2 and t3? t1 t2 t3 A NO2Cl was removed temperature was increased NO2Cl was added B temperature was decreased NO2Cl was added NO2 was added C NO2 was removed temperature was increased NO2Cl was added D NO2Cl was removed NO2Cl was added temperature was decreased concentration of NO2Cl time

7 8873/01 [Turn over 13 Use of the Data Booklet is relevant to this question. Hypothetically, N4 could be formed from nitrogen gas by the following reaction. 2N2(g)  N4(g) ∆H By considering the bonds broken and bonds formed, as well as the structure of N4 given below, what would be the value of H for the above reaction? A +140 kJ mol1 B −140 kJ mol1 C +928 kJ mol1 D −928 kJ mol1 14 The lattice energy of calcium chloride is numerically greater than that of potassium bromide. Which statements could explain this observation? 1 The chlorine atom is more electronegative than the bromine atom. 2 The charge on the calcium ion is greater than that of the potassium ion. 3 The Ca–Cl bond length is shorter than that of K–Br. A 2 only B 1 and 2 only C 1 and 3 only D 2 and 3 only

8 8873/01 [Turn over 15 Reaction pathway diagrams, P and Q refer to two different types of reaction. Which row correctly identifies the enthalpy change shown in P and Q? P Q A lattice energy enthalpy of formation B lattice energy enthalpy of combustion C enthalpy of formation enthalpy of combustion D enthalpy of formation lattice energy 16 Which statement is true about the elements in Group 1 of the Periodic Table? A They react with water to give off oxygen gas. B They are more readily oxidised down the group. C Sodium is less electronegative than caesium. B They can conduct electricity in the solid state, but not in liquid state. 17 Which statement about the chlorides of Period 3 elements is incorrect? A The pH of the solutions of chlorides generally increases across the period. B The extent of hydrolysis of the chlorides increase across the period. C When limited amount of water is added to the covalent chlorides, they give acidic white fumes. D Adding NaOH(aq) to a solution of AlCl3 produces a white precipitate which is soluble in an excess of NaOH. enthalpy reaction pathway P enthalpy reaction pathway Q reactants products reactants products

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