Candidate Number. Other Names These questions relate to your investigation of

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1 Centre Number Surname Section A Candidate Number ther Names These questions relate to your investigation of Notice to Candidate. The work you submit for assessment must be your own. If you copy from someone else or allow another candidate to copy from you, or if you cheat in any other way, you may be disqualified. Candidate Declaration. Use the I have Task read Sheet and understood and your the Notice results to Candidate to answer and the can confirm questions. that I have produced the attached work without assistance other than that which is acceptable under the scheme of assessment. Answer all questions in the spaces provided. Candidate Date Signature For Teacher s Use Section Mark PSA Task Section A Section B Chemistry Unit 6T Written Test General Certificate of Education Advanced Level Examination June 2015 A2 Investigative Skills Assignment For submission by 15 May 2015 For this paper you must have: l the Periodic Table/Data Sheet, provided at the end of this paper l your Task Sheet and your Candidate Results Sheet l a ruler with millimetre measurements l a calculator. CHM6T/Q15/test Time allowed l 1 hour TTAL (max 50) Instructions l Use black ink or black ball-point pen. l Fill in the es at the top of this page. l Answer all questions. l You must answer the questions in the spaces provided. Do not write around each page or on blank pages. l Do all rough work in this book. Cross through any work you do not want to be marked. Information l The marks for questions are shown in brackets. l The maximum mark for this paper is 30. l You are expected to use a calculator, where appropriate. l You will be marked on your ability to: organise information clearly use scientific terminology accurately. Details of additional assistance (if any). Did the candidate receive any help or information in the production of this work? If you answer yes give the details below or on a separate page. Yes No Teacher Declaration: I confirm that the candidate s work was conducted under the conditions laid out by the specification. I have authenticated the candidate s work and am satisfied that to the best of my knowledge the work produced is solely that of the candidate. Signature of teacher... Date... As part of AQA s commitment to assist students, AQA may make your coursework available on a strictly anonymous basis to teachers, examining staff and students in paper form or electronically, through the Internet or other means, for the purpose of indicating a typical mark or for other educational purposes. In the unlikely event that your coursework is made available for the purposes stated above, you may object to this at any time and we will remove the work on reasonable notice. If you have any concerns please contact AQA. To see how AQA complies with the Data Protection Act 1988 please see our Privacy Statement at aqa.org.uk /E5 CHM6T/Q15/test

2 2 Section A These questions are about the task, determination of an enthalpy change. You should use your Task Sheet and your Candidate Results Sheet to answer these questions. Answer all questions in the spaces provided. 1 Use your results from Part 1 to plot a graph of temperature (y-axis) against time on the grid for Part 1 on page 3. Draw two straight lines of best fit and extrapolate both lines past the fourth minute. Determine the temperature change that would have occurred at the fourth minute. Use your results from Part 2 to plot a graph of temperature (y-axis) against time on the grid for Part 2 on page 3. Draw two straight lines of best fit and extrapolate both lines past the fourth minute. Determine the temperature change that would have occurred at the fourth minute. [5 marks] Temperature change at the fourth minute for Part 1... Temperature change at the fourth minute for Part Use the temperature change from Part 1 to calculate a value for the molar enthalpy change for the reaction between sodium carbonate (M r = 106.0) and hydrochloric acid, that was in excess. Assume that the reaction mixture has a density of 1.00 g cm 3 and a specific heat capacity of 4.18 J K 1 g 1. [3 marks]

3 3 Part 1 Temperature / ºC Time / mins Part 2 Temperature / ºC Time / mins Turn over

4 4 3 Use the temperature change from Part 2 to calculate a value for the molar enthalpy change for the reaction between sodium hydrogencarbonate (M r = 84.0) and hydrochloric acid, that was in excess. Assume that the reaction mixture has a density of 1.00 g cm 3 and a specific heat capacity of 4.18 J K 1 g 1. [2 marks] 4 Sodium hydrogencarbonate decomposes as shown by the equation: 2NaHC 3 (s) Na 2 C 3 (s) + H 2 (I) + C 2 (g) Use your answers to Question 2 and Question 3, together with an enthalpy cycle, to calculate a value for the enthalpy change when one mole of NaHC 3 decomposes. Show your working. (If you were unable to calculate values in Question 2 and Question 3, you can assume that the molar enthalpy change for the reaction between sodium carbonate and excess hydrochloric acid is 20.1 kj mol 1 and that the molar enthalpy change for the reaction between sodium hydrogencarbonate and excess hydrochloric acid is kj mol 1. These are not the correct values.) [4 marks]

5 5 5 A data source gives the value for the enthalpy change of the reaction between sodium hydrogencarbonate and excess hydrochloric acid as kj mol 1. Calculate the percentage difference between this value and your answer to Question 3. [1 mark] 6 Sodium hydrogencarbonate decomposes slowly to sodium carbonate on standing. The sample of sodium hydrogencarbonate was weighed, and then left in an open beaker overnight before doing the experiment. State the effect this decomposition would have on the temperature change for Part 2. Give two reasons for your answer. [3 marks] Effect... Reason 1... Reason Turn over for the next question Turn over

6 6 Section B Answer all questions in the spaces provided. For many years, swimming pool water has been treated with chlorine gas. The chlorine is added to kill any harmful bacteria unintentionally introduced by swimmers. Pool managers are required to check that the chlorine concentration is high enough to kill the bacteria without being a health hazard to the swimmers. 7 When chlorine reacts with water in the absence of sunlight, the chlorine is both oxidised and reduced and an equilibrium is established. 7 (a) Write an equation for this equilibrium. For each chlorine-containing species in the equation, write the oxidation state of chlorine below the species. [2 marks] 7 (b) The pool manager maintains the water at a ph slightly greater than 7.0 Explain how this affects the equilibrium established when chlorine is added to water. [2 marks]

7 7 7 (c) Explain why chlorine is used to kill bacteria in swimming pools, even though chlorine is toxic. [2 marks] 8 A solution of chlorine in water is acidic. Swimming pool managers maintain pool water at a constant ph by using a buffer. They do so by adding sodium hydrogencarbonate and sodium carbonate. 8 (a) Hydrogen carbonate ions (HC 3 ) act as a weak acid in aqueous solution. Write an equation for this equilibrium. [1 mark] 8 (b) Use the equation in Question 8 (a) to explain how a solution containing sodium hydrogencarbonate and sodium carbonate can act as a buffer when small amounts of acid or small amounts of alkali are added. [3 marks] Turn over

8 8 9 The water used to fill the swimming pool contains some iron(iii) ions. The pool manager needs to measure the concentration of these ions in the water supply. Iron(III) ions react with thiocyanate ions to form an iron(iii) complex that has a deep red colour. Suggest how a colorimeter could be used to measure the concentration of the iron(iii) complex in this solution. [2 marks] 12 END F QUESTINS

9 9 Table A Infrared absorption data Bond Wavenumber /cm 1 N H (amines) H (alcohols) C H H (acids) C N C C C C C C GCE Chemistry Data Sheet Table B 1 H n.m.r. chemical shift data Type of proton δ/ppm RH RCH RNH R2CH R3CH R C C H R C H RCH2Cl or Br R C C H R H C C R C H R C H Table C 13 C n.m.r. chemical shift data Type of carbon δ/ppm C C 5 40 R C Cl or Br R C C R C N alcohols, C ethers or esters C C R C N R C esters or acids R C aldehydes or ketones Turn over

10 10 The Periodic Table of the Elements (1) (2) 6.9 Li lithium Na sodium K potassium Rb rubidium Cs caesium 55 [223] Fr francium Be beryllium Mg magnesium Ca calcium Sr strontium Ba barium 56 [226] Ra radium 88 relative atomic mass symbol name atomic (proton) number 1.0 H hydrogen 1 (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) 45.0 Sc scandium Y yttrium La * lanthanum 57 [227] Ac actinium Ti titanium Zr zirconium Hf hafnium 72 [267] Rf rutherfordium 104 Key 50.9 V vanadium Nb niobium Ta tantalum 73 [268] Db dubnium Cr chromium Mo molybdenum W tungsten 74 [271] Sg seaborgium Mn manganese 25 [98] Tc technetium Re rhenium 75 [272] Bh bohrium Fe iron Ru ruthenium s osmium 76 [270] Hs hassium Co cobalt Rh rhodium Ir iridium 77 [276] Mt meitnerium Ni nickel Pd palladium Pt platinum 78 [281] Ds darmstadtium Cu copper Ag silver Au gold 79 [280] Rg roentgenium Zn zinc Cd cadmium Hg mercury 80 (13) (14) (15) (16) (17) 10.8 B boron Al aluminium Ga gallium In indium Tl thallium C carbon Si silicon Ge germanium Sn tin Pb lead N nitrogen P phosphorus As arsenic Sb antimony Bi bismuth oxygen S sulfur Se selenium Te tellurium 52 [209] Po polonium F fluorine Cl chlorine Br bromine I iodine 53 [210] At astatine 85 Elements with atomic numbers have been reported but not fully authenticated (18) 4.0 He helium Ne neon Ar argon Kr krypton Xe xenon 54 [222] Rn radon 86 * Lanthanides Actinides Ce cerium Th thorium Pr praseodymium Pa protactinium Nd neodymium U uranium 92 [145] Pm promethium 61 [237] Np neptunium Sm samarium 62 [244] Pu plutonium Eu europium 63 [243] Am americium Gd gadolinium 64 [247] Cm curium Tb terbium 65 [247] Bk berkelium Dy dysprosium 66 [251] Cf californium Ho holmium 67 [252] Es einsteinium Er erbium 68 [257] Fm fermium Tm thulium 69 [258] Md mendelevium Yb ytterbium 70 [259] No nobelium Lu lutetium 71 [262] Lr lawrencium 103 Copyright 2015 AQA and its licensors. All rights reserved.

This resource contains three different versions of the periodic table, including a blank one for colouring!

Teaching notes This resource contains three different versions of the periodic table, including a blank one for colouring! It also contains tables of the Group 0, 1 and 7 elements with a few columns for