2024 YIJC JC2 H1 CHEM PE P2 Student s Copy)

©YIJC [Turn over YISHUN INNOVA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 1 CANDIDATE NAME CG H1 GROUP 1 / 2 / 3 CHEMISTRY Paper 2 Structured and Free Response Questions Candidates answer on the Question Paper. Additional Materials: Data Booklet 8873/02 10 September 2024 2 hours READ THESE INSTRUCTIONS FIRST This document consists of 28 printed pages and 4 blank pages. For Examiner’s Use Section A 1 / 9 2 / 8 3 / 10 4 / 10 5 / 12 6 / 11 Section B 7 or 8 / 20 Penalty units significant figures Total / 80 Write your name and class in the spaces at the top of this page. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all questions. Section B Answer one question. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question or part question.

©YIJC [Turn over 2 Section A Answer all the questions in this section in the spaces provided. 1 (a) A, B and C are three consecutive period 3 elements in the periodic table. D is an isotope of one of the elements. Table 1.1 shows information on the number of protons, neutrons and electrons in species of A, B, C and D. Table 1.1 species protons neutrons electrons A 15 16 15 B2− 16 17 q C 17 18 17 D− 17 17 18 (i) Deduce the value of q. [1] (ii) Identify the element, A, B or C, that is isotopic to D. Explain your answer. [2]

©YIJC [Turn over 3 (b) Element E is a Period 3 element. The first nine successive ionisation energies, in kJ mol−1, of element E are given in Table 1.2. Table 1.2 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 1251 2298 3822 5159 6542 9362 11018 33604 38600 (i) With reference to E, explain what is meant by first ionisation energy of E. [1] (ii) Use the information given in Table 1.2 to deduce the identity of element E. Explain your answer. [2]

©YIJC [Turn over 4 (c) Sulfur is also an element found in the Period 3 of the Periodic Table. (i) Complete the diagram to show the arrangement of electrons in the orbitals of a sulfur atom. ↿⇂ 1s 2s 2p 3s 3p [1] (ii) State and explain the general trend in first ionisation energy across Period 3 elements. Explain why sulfur does not follow this general trend. [2] [Total: 9]

©YIJC [Turn over 5 BLANK PAGE

©YIJC [Turn over 6 2 (a) Magnesium exists as three principal isotopes, 24Mg, 25Mg and 26Mg. isotope relative isotopic mass natural abundance (%) 24Mg 23.99 78.99 25Mg 24.99 10.00 26Mg 25.98 11.01 Use the data to calculate the relative atomic mass of magnesium to two decimal places. [1] (b) Gastric juice is a thin, acidic digestive fluid secreted by glands in the mucous membrane that lines the stomach. An average adult produces about 1 mole of gastric juice when pain is experienced. 1 mole of gastric juice contains 0.002 mole of hydrochloric acid. An antacid is a substance which counteracts stomach acidity by raising the pH. One example is Brand F antacid which contains 20% magnesium carbonate, MgCO3. One tablet of antacid in Brand F has a mass of 325 mg. (i) Write a balanced equation for the reaction of Brand F antacid with hydrochloric acid. [1] (ii) Calculate the amount of magnesium carbonate in one tablet of Brand F antacid. [1] (iii) Calculate the number of tablets a person has to consume to remove the gastric juice. [2]

©YIJC [Turn over 7 (c) Compound G contains carbon, hydrogen and oxygen only. G contains 66.7% by mass of carbon, 11.1% by mass of hydrogen and 22.2% by mass of oxygen. The relative molecular mass, Mr, of G is 72. (i) Calculate the empirical formula and deduce the molecular formula of G. [2] (ii) Compound G is a ketone. Draw the displayed formula of G. [1] [Total: 8]

©YIJC [Turn over 8 3 (a) Phosphorus reacts with fluorine to form phosphorus trifluoride, PF3, and phosphorus pentafluoride, PF5. (i) Draw the dot -and-cross diagram for one molecule of PF 3. Show only the outer shell electrons. [1] (ii) State the bond angle in a molecule of PF3 and name the shape of the molecule. Explain your answers using Valence Shell Electron Pair Repulsion Theory. [3] (iii) Deduce whether PF3 is a polar molecule. Explain your answer. [2] (iv) Nitrogen reacts with fluorine to form NF3 only. Explain why PF5 exists whereas NF5 does not exist. [1]

©YIJC [Turn over 9 (b) Use of the Data Booklet is relevant to this question. Predict the colours of the final solution when • KI(aq) is added to Cl2(aq), • KCl(aq) is added to Br2(aq), • KBr(aq) is added to I2(aq). Write equations for any reactions that occur. State clearly if no reaction occurs. [3] [Total: 10]

©YIJC [Turn over 10 4 (a) Air is a mixture of mainly nitrogen and oxygen that does not react at room temperature. Gas molecules move about in the container in which they are enclosed with different amount of energy. (i) Sketch a graph to show the energy distribution of gas molecules at room temperature. Label this curve T. [1] (ii) On the same axes sketch the energy distribution of the same gas molecules at a temperature of 150oC. Clearly label this curve 150oC. [1] At higher temperatures nitrogen and oxygen do react. (iii) Indicate an activation energy, Ea, on your graph. [1] (iv) Use the sketches that you have drawn and collision theory to explain why an increase in temperature causes an increase in the rate constant and rate of a reaction. [2]