2024 Y5 DHS H2 Chemistry Timed Practice 1

1 © DHS 2024 DUNMAN HIGH SCHOOL 2024 YEAR 5 H2 CHEMISTRY TIME PRACTICE 1 Mole Concept, Redox & Atomic Structure Name : Date: ___________ Duration: 50 minutes Class : Section A – Multiple Choice Questions Answer all questions. Write your answers in the boxes below. MCQ No. 1 2 3 4 5 Your Answer 1 Use of Data Booklet is relevant to this question. Which statement about a 20.3 g sample of Co2(SO4)3 (Mr = 406) is incorrect? A It contains 1.5 × 1023 ions. B It contains 0.1 mol of Co3+ ions. C It contains 14.5% of cobalt by mass. D It contains 47.3% of oxygen by mass. 2 In an experiment, Fe3+ oxidises X3+(aq) in acidic medium, while itself is reduced to Fe2+. 20.0 cm3 of 0.0120 mol dm –3 X3+(aq) was found to require 24.00 cm 3 of 0.0300 mol dm –3 Fe3+ for complete oxidation. What is the formula of the X-containing species formed? A XO+ B XO2+ C XO22+ D X2O22+ Qn MCQ Q6 Q7 Q8 Q9 Total % Grade Marks 5 6 3 6 10 30

2 © DHS 2024 3 The successive ionisation energies (IE) of two elements, M and N, are given below. IE / kJ mol–1 1st 2nd 3rd 4th 5th 6th 7th 8th M 550 1065 4138 5500 6910 8760 10230 11800 N 1140 2103 3470 4560 5760 8550 9940 18600 What is the most likely formula of the compound that is formed between M and N? A MN B MN2 C M2N D M3N2 4 When passed through an electric field, the 1H+ ion is deflected as shown below. Which of the above beams represents the deflection for the ion 2D–? (D = H1 2 ) 5 Use of Data Booklet is relevant to this question. Some isotopes are unstable and undergo nuclear (radioactive) reactions. In one type of reaction, an unstable nucleus assimilates an electron from an inner orbital of its electron cloud. The net effect is the conversion of a proton and an electron into a neutron. 10 1 -1p + e → 1 0n Which of the following is an example of this type of reaction? A 11C → 12C B 111I → 111Te C 76Br → 75Br D 76Kr → 75Br A B C D 1H+ ion 4o 4 o + − source

3 © DHS 2024 Section B – Structured Questions Answer all questions in the space provided. Marks will be allocated for relevant working. 6 Verdigris was the most vibrant green pigment available and was frequently used in painting until the 19th century. Verdigris is resistant to fading when it is exposed to light, as numerous examples of the paintings show. This pigment was made by hanging copper foil over boiling vinegar. (a) During the preparation of verdigris, copper atoms are oxidised to copper( II) ions , Cu 2+. Oxygen is reduced to water in acidic medium. (i) Write half–equations for both the reduction and oxidation reactions. Hence write the balanced equation for the reaction between Cu and O2. Reduction: ………………………………………………………………………………...…… Oxidation: ……………………………………………………………………………………... Overall: ..…………………………………………………………………………………[2] (ii) Given that 5 g of copper foil was boiled in vinegar to produce verdigris, calculate the volume of oxygen used in the reaction at room temperature and pressure. [2]

4 © DHS 2024 (b) (i) A sample of verdigris has the formula [(CH 3COO)2Cu]2.Cu(OH)2.xH2O. 50 g of the sample contains 16.3% of water by mass. Calculate the number of moles of [(CH 3COO)2Cu]2.Cu(OH)2 present in 50 g of the verdigris sample. [Mr of [(CH3COO)2Cu]2.Cu(OH)2 = 460.5] [1] (ii) Hence or otherwise, calculate the value of x in the formula. [1] [Total: 6]

5 © DHS 2024 7 10 cm3 of a gaseous hydrocarbon, C xHy, was exploded with an excess of oxygen. There was a contraction of 30 cm 3. When the resulting gaseous mixture was treated with aqueous sodium hydroxide, there was a further contraction of 40 cm3. Given that all gas volumes were measured at r.t.p., determine the molecular formula of the hydrocarbon. Show your working clearly. [3] [Total: 3]

6 © DHS 2024 8 (a) [Cr(OH)4]‒ reacts with hydrogen peroxide, H2O2, under alkaline conditions as shown in the below equation: 2[Cr(OH)4]‒ + 3H2O2 + 2OH‒ → 2CrO4 2‒ + 8H2O State the changes in oxidation numbers that occur during this reaction. Hence identify the role of hydrogen peroxide when it reacts with [Cr(OH)4]‒. ………………………………………………………………………………………....……………….. ………………………………………………………………………………………....……………….. ………………………………………………………………………………………....……………….. ………………………………………………………………………………………....…………….[2] (b) The percentage purity of a sample of potassium dichromate, K 2Cr2O7, was determined by volumetric analysis. 1.65 g of K2Cr2O7 (Mr = 294.2) was added to excess aqueous potassium iodide, KI, in acidic medium. The solution was made up to 250.0 cm3 with distilled water. Cr2O7 2‒ + 6I‒ + 14H+ → 3I2 + 2Cr3+ + 7H2O A 20.0 cm3 aliquot was withdrawn and titrated against 24.8 g dm‒3 aqueous sodium thiosulfate pentahydrate, Na2S2O3.5H2O (Mr = 248.2). 2Na2S2O3 + I2 → Na2S4O6 + 2NaI The following results were obtained. Titration 1 2 3 Initial burette reading / cm3 0.40 0.10 0.10 Final burette reading / cm3 25.55 24.95 25.05 Volume of Na2S2O3.5H2O used / cm3 25.15 24.85 24.95 (i) From the titration results above, obtain a suitable volume of Na2S2O3.5H2O which reacted with the iodine in the 20.0 cm3 aliquot. Show clearly how you obtained this volume. [1]

7 © DHS 2024 (ii) Using your answer to (b)(i), calculate the percentage purity of the sample of potassium dichromate. [3] [Total: 6]

8 © DHS 2024 9 (a) While glutamic acid is often used as a flavour enhancer in the form of its sodium salt, monosodium glutamate (MSG), other cations such as K + have also been used to form glutamate salts. (i) Write the full electronic configuration of K+. ………………………………………………………………………………………………..[1] (ii) State and explain how the ionic radius of K+ compares to that of Na+. …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... ……………………………………………………………………………………………….. [2] (iii) Sketch, on separate diagrams, all the occupied orbitals in the outermost electron shell of K+. Label the orbitals clearly. [2]

9 © DHS 2024 (b) Fig. 9.1 shows a sketch of the second ionisation energy (2 nd IE) of seven consecutive elements from O to U. log (2nd IE) O P Q R S T U V W elements Fig. 9.1 (i) By comparing the 2nd IE of Q and R, deduce which Group in the Periodic Table element Q is from. …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... ………………………………………………………………………………………………..[2] (ii) By considering the outermost shell electronic configurations of S+ and T+, explain why there is a drop in 2nd IE from S to T. S+: ………………………………. T+: ………………………………. …………………………………………………………………………………………………... …………………………………………………………………………………………………... ………………………………………………………………………………………………..[2] (iii) On Fig. 9.1, co mplete the sketch to indicate the 2 nd IE of the next two consecutive elements, V and W. [1] [Total:10]

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