NYJC H1 Chemistry P2

[Turn over NANYANG JUNIOR COLLEGE JC 2 Preliminary Examinations Higher 1 CANDIDATE NAME CLASS TUTOR’S NAME CHEMISTRY 8872/02 Paper 2 22 September 2014 2 hours Candidates answer on the Question Paper Additional Materials: Answer Paper Data Booklet READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all questions. Section B Answer any two questions on separate answer paper. A Data Booklet is provided. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 / 20 2 / 8 3 / 12 Total / 40 This document consists of 14 printed pages and 0 blank page.

2 H1 Chemistry 8872/02 NYJC J2/14 PX For examiner’s use only Section A Answer all the questions in this section in the spaces provided. 1 A gas is said to exhibit ideal gas behavior if it obeys the ideal gas equation pV = nRT where p = pressure of gas in atm, V = volume of gas in dm3, n = amount of gas (mol), R = 0.0821 dm3 atm K1 mol1 (a constant), and T = temperature in K. (a) A 2.00 dm3 flask contains oxygen at 1.20 atm and 314 K. (i) Use the ideal gas equation to find the amount of oxygen in the flask. (ii) Hence calculate the mass of oxygen in the flask. [3]

3 H1 Chemistry 8872/02 NYJC J2/14 PX For examiner’s use only (b) The data below were derived using the ideal gas equation for 1 g of hydrogen. p / atm V / dm3 T / K 1.0 12.3 300 1.4 17.6 600 2.1 5.9 300 3.6 6.8 600 4.8 2.6 300 5.6 4.4 600 (i) How does p vary with V for 1 g of hyd rogen at a con stant temperature? .......................................................................................................... (ii) Sketch the graphs of p against V for 1 g of hydrogen at 300 K and at 600 K on the same axes below. Label each graph. V p 0

4 H1 Chemistry 8872/02 NYJC J2/14 PX For examiner’s use only (iii) Sketch the graph of pV against p for 1 g of hydrogen at 450 K. [4] (c) Oxygen gas behaves ideally because the intermolecular forces of attraction are very weak. On the other hand, the intermolecular forces in methanol vapour cause it to behave less ideally. (i) What are the intermolecular forces of attraction in each substance? Oxygen .................................................................................................. Methanol vapour .................................................................................... (ii) Draw a labelled diagram to show the forces of attraction between two molecules of methanol in the vapour state. [5] p pV 0

5 H1 Chemistry 8872/02 NYJC J2/14 PX For examiner’s use only (d) The ideal gas equation can be used to derive a rela tionship for the relative molecular mass of a gas. r mRTM pV where m is the mass of the gas in grams. A 0.458 g sample containing a gaseous mixture of AlCl 3 and Al2Cl6 takes up a volume of 54 cm3 at a temperature of 98 °C and a pressure of 1 atm. (i) Draw a dot-and-cross diagram for the AlCl3 molecule. (ii) Draw the structural formula of the Al2Cl6 molecule. (iii) Calculate the average Mr of the mixture. (iv) Hence calculate the percentage by mass of Al2Cl6 in the mixture. [8] [Total: 20]

6 H1 Chemistry 8872/02 NYJC J2/14 PX For examiner’s use only 2 (a) Explain what is meant by the term order of reaction. .......................................................................................................................... ..................................................................................................................... [1] (b) Hydrogen peroxide reacts with iodide ions in acidic solution as shown below. H2O2(aq) + 2H+(aq) + 2I(aq)  2H2O(l) + I2(aq) The results of some inv estigations of the rate of this reaction are shown below. Experiment number [H2O2] / mol dm3 [H+] / mol dm3 [I] / mol dm3 Relative initial rate / mol dm3 s1 1 0.030 0.050 0.060 1.80 2 0.020 0.060 0.050 1.00 3 0.0375 0.060 0.060 2.25 4 0.025 0.060 0.050 1.25 (i) Use the above data to determine the order of reaction with respect to  H2O2  H+  I (ii) Hence, write a rate equation for the above reaction. ............................................................................................................... [4]

7 H1 Chemistry 8872/02 NYJC J2/14 PX For examiner’s use only (c) With the aid of a sketch of the Boltzmann distribution, expla in how an increase in temperature increases the rate of a chemical reaction. .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... [3] [Total: 8]

8 H1 Chemistry 8872/02 NYJC J2/14 PX For examiner’s use only 3 Esters are compounds which provide the flavour of many fruits and the perfumes of many flowers. (a) The ester CH3(CH2)2CO2CH3 contributes to the aroma of apples. (i) State the reagents and conditions needed for the hydrolysis of this ester. ............................................................................................................... (ii) Write the equation for the hydrolysis of this ester. ............................................................................................................... ............................................................................................................... (iii) Apart from their use as perfumes and food flavourings, state one major commercial use of esters. ............................................................................................................... ............................................................................................................... [3] (b) Leaf alcohol is a stereoisomer that can form when insects such as caterpillars eat green leaves. C C H CH2 CH3CH2 H CH2 OH (i) Draw the other stereoisomer of leaf alcohol. (ii) Draw the displayed formula of the ester for med when leaf alcohol reacts with ethanoic acid. [3]

9 H1 Chemistry 8872/02 NYJC J2/14 PX For examiner’s use only (c) (i) Deduce the relative molecular mass, Mr, for leaf alcohol. (ii) Leaf alcohol was reacted to form a product with an Mr value 18 units less. Suggest a structure for this product and deduce th e type of reaction that took place. [3] (d) Describe a simple chemical test to distinguish between leaf alcohol and your product in (c)(ii). Draw the structures of the products of any reactions that occur. [3] [Total: 12]

10 H1 Chemistry 8872/02 NYJC J2/14 PX Section B Answer any two questions from this section on separate answer paper. 4(a) Sodium hydrogencarbonate decomp