H1 Chem P2 SAJC 2024 QP

1 [TURN OVER ST ANDREW’S JUNIOR COLLEGE PRELIMINARY EXAMINATIONS HIGHER 1 CANDIDATE NAME CLASS 2 3 H1 CHEMISTRY 8873 / 02 Paper 2 Structured Questions 27 August 2024 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your centre number, index number, name and class at the top of this page. Write in dark blue or black pen. You may use a HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. A Data Booklet is provided. Section A Answer all the 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. Question Number Total Marks Marks Obtained SECTION A 1 14 2 7 3 9 4 30 SECTION B 5 20 6 20 TOTAL 80 This document consists of 28 printed pages (including this cover page).

2 [TURN OVER Section A Answer all the questions in this section in the spaces provided. 1 This is a question about Group 14 elements and its compounds. (a) (i) A sample of silicon contains three isotopes, as shown in Table 1.1. Table 1.1 Isotope Relative Isotopic mass Percentage abundance. % 28Si 27.976 92.22 29Si 28.976 4.69 30Si 29.973 3.09 Calculate the relative atomic mass of silicon in this sample, giving your answer to two decimal places. [2] (ii) Complete the electronic configuration for silicon. [1] 1s2 ………………………………………………………………………………... (iii) Explain why second ionisation energy of silicon is lower than that of aluminium. [2] ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………...

3 [TURN OVER 1 (b) When carbon tetrachloride, CCl4, and silicon tetrachloride, SiCl4, were added to water, the following observations were seen. carbon tetrachloride Forms two immiscible layers silicon tetrachloride White solid and steamy fumes (i) Write a balanced equation for the reaction of SiCl4 with water. [1] ……………………………………………………………………………………………... (ii) CCl4 has no reaction with water. Suggest an explanation for the inertness of CCl4 to water. [1] ……………………………………………………………………………………………... ……………………………………………………………………………………………... (iii) Explain why CC l4 forms two immiscible layers with water when they are mixed. [2] ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………...

4 [TURN OVER 1 (c) Due to carbon’s ability to form strong multiple bonds, it can form different allotropes like graphene and fullerene. Graphene is an allotrope of carbon that occurs as two-dimensional sheets while fullerenes are molecules of carbon atoms with hollow shapes. An example of a spherical fullerene is buckminsterfullerene, C60, while carbon nanotube (CNT) is a type of cylindrical fullerene. Buckminsterfullerene has low melting point and is slippery while CNT, like graphene, has high tensile strength and is an excellent conductor of electricity. (i) Graphene is a nanomaterial. Define what is meant by the term nanomaterial. [1] …………………………………………………………………………………… …………………………………………………………………………………… ………........................................................................................................ (ii) Draw a diagram to illustrate the structure of graphene. [1]

5 [TURN OVER 1 (c) (iii) Explain how carbon nanotube is an excellent conductor of electricity and has high tensile strength. [2] ……………………………………………………………………………………………... ……………………………………………………………………………………………... (iv) Suggest why buckminsterfullerene is a good lubricant. [1] ……………………………………………………………………………………………... ……………………………………………………………………………………………... [Total: 14]

6 [TURN OVER 2 Propanone, CH3COCH3, reacts with iodine, I2, in the presence of an acid catalyst. An experiment is performed using 1.00 mol dm–3 of I2 and 1.00 mol dm–3 H+(aq) where concentration of CH3COCH3 is monitored over time. The same experiment was then repeated using 0.500 mol dm-3 H+(aq) instead. The results obtained are used to plot the graph below. Fig 2.1 0 0.01 0.02 0.03 0.04 0.05 0.06 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 [CH3COCH3] /mol dm–3 time / min [H+]= 0.5 mol dm–3 [H+]= 1.0 mol dm–3

7 [TURN OVER 2 (a) It was found that the reaction is zero order with respect to [I2]. Define the term order of reaction. [1] ……………………………………………………………………………………………............. ..........……………………………………………………………………………………………... (b) (i) Use the graph, Fig 2.1, to determine the order of reaction with respect to [CH3COCH3] and [H+] respectively. [2] …………………………………………………………………………………… …………………………………………………………………………………… ………...………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… (ii) Write the rate equation for this reaction. Hence, calculate the value of rate constant, k. Include the units. [2] …………………………………………………………………………………… ………...………………………………………………………………………….

8 [TURN OVER 2 (c) Other halogens, like chlorine and bromine, can also react with propanone in similar reactions as iodine. Describe and explain how the reactivity of halogens varies down the group. Include relevant data from the Data Booklet in your answer. [2] …………………………………………………………………………………… …………………………………………………………………………………… ………...………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… [Total: 7]

9 [TURN OVER 3 A sample of sodium nitrite, NaNO2, was analysed by titrating with yellow aqueous cerium(IV) ions, Ce4+. The experimental procedures for this analysis were as follows. • 0.140 g of impure NaNO 2 was dissolved in deionised water to form a colourless solution. It was then transferred to a 100 cm3 volumetric flask and top up to the mark with more deionised water. • 25.0 cm3 of this solution required 22.05 cm3 of 0.0400 mol dm–3 Ce4+(aq) to reach the end-point. During the titration, Ce 4+ was reduced to colourless Ce3+ while nitrite ion was oxidised to form colourless nitrate ion, NO3–. (a) (i) Draw a dot-and-cross diagram of NaNO2. [2] (ii) Construct the ionic equation for the reaction between sodium nitrite and cerium(IV) ions. [1] ……………………………………………………………………………………………... (iii) Calculate the percentage purity of this sample of NaNO2. [3]

10 [TURN OVER 3 (a) (iv) Predict the colour change at the end-point of this titration. [1] ……………………………………………………………………………………………... (b) Suggest and explain the difference in the ionic radii of Ce4+ and Ce3+. [2] …………………………………………………………………………………………… …………………………………………………………………………………...……… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… [Total: 9]