AS CHEMISTRY Paper 1 Inorganic and Physical Chemistry

*JUN* IB/M/Jun22/E7 7404/1 For Examiner’s Use Question Mark 1 2 3 4 5 6 7 8 Section B TOTAL Time allowed: 1 hour 30 minutes Materials For this paper you must have: • the Periodic Table/Data Sheet, provided as an insert (enclosed) • a ruler with millimetre measurements • a scientific calculator, which you are expected to use where appropriate. Instructions • Use black ink or black ball-point pen. • Fill in the boxes at the top of this page. • Answer all questions. • You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages. • If you need extra space for your answer(s), use the lined pages at the end of this book. Write the question number against your answer(s). • All working must be shown. • Do all rough work in this book. Cross through any work you do not want to be marked. Information • The marks for questions are shown in brackets. • The maximum mark for this paper is 80. Advice You are advised to spend about 65 minutes on Section A and 25 minutes on Section B. Please write clearly in block capitals. Centre number Candidate number Surname Forename(s) Candidate signature I declare this is my own work. AS CHEMISTRY Paper 1 Inorganic and Physical Chemistry Downloaded by Edith scott () lOMoARcPSD| 2 *02* IB/M/Jun22/7404/1 Do not write outside the Section A box Answer all questions in this section. 0 1 This question is about ionisation energies of Group 2 elements. 0 1 . 1 Explain why the first ionisation energy of the Group 2 elements decreases down the group. [2 marks] 0 1 . 2 Give an equation, including state symbols, to represent the process that occurs when the third ionisation energy of magnesium is measured. [1 mark] 0 1 . 3 Explain why the third ionisation energy of magnesium is much higher than the second ionisation energy of magnesium. [2 marks] 5 Downloaded by Edith scott () lOMoARcPSD| 3 *03* Turn over ► IB/M/Jun22/7404/1 Do not write outside the box 0 2 This question is about acid–base titrations. Citric acid reacts with sodium hydroxide. C6H8O7(aq) + 3NaOH(aq) → Na3C6H5O7(aq) + 3H2O(l) 0 2 . 1 A student makes a solution of citric acid by dissolving some solid citric acid in water. Describe a method to add an accurately known mass of solid to a beaker to make a solution. [2 marks] 0 2 . 2 The student dissolves 0.834 g of citric acid in water and makes the solution up to 500 cm3 Calculate the concentration, in mol dm–3, of citric acid in this solution. [3 marks] Concentration mol dm–3 Downloaded by Edith scott () lOMoARcPSD| 4 *04* IB/M/Jun22/7404/1 Do not write outside the box 0 2 . 3 The student uses this method to complete a titration. • Rinse a burette with distilled water. • Fill the burette with sodium hydroxide solution. • Use a measuring cylinder to transfer 25 cm3 of the citric acid solution into a conical flask. • Add 5 cm3 of indicator. • Slowly add the sodium hydroxide solution from the burette into the conical flask. • Add the sodium hydroxide solution dropwise near the end point until the indicator just changes colour. • Repeat the titration to get concordant results. The method used by the student includes three practical steps that will lead to an inaccurate final result. For each of these three steps • identify the mistake • explain why it is a mistake • suggest how the mistake can be overcome.