A-level CHEMIS T RY Paper 1 Inorganic and Physical Chemistry

A-level CHEMIS T RY Paper 1 Inorganic and Physical Chemistry Monday 10 June 2024 Morning Time allowed: 2 hours Materials For this paper you must have: • the Periodic Table/Data Booklet, 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 105. Answer all questions in the spaces provided. box This question is about atomic structure. 0 1 . 1 In 1897 JJ Thomson discovered the electron. He suggested that atoms were positively charged spheres with electrons embedded within them. Figure 1 represents an atom using Thomson’s model. Figure 1 Suggest the identity of this atom. Give two differences between the modern model of an atom and the Thomson model of an atom. [3 marks] Identity Difference 1 Difference 2 0 1 . 2 Tellurium has a relative atomic mass of 127.6 Iodine has a relative atomic mass of 126.9 Define relative atomic mass. Suggest one property of tellurium that justifies its position before iodine in the modern Periodic Table. [3 marks] Definition Justification . A sample of tellurium is analysed in a time of flight (TOF) mass spectrometer using electron impact ionisation. Give an equation, including state symbols, for this ionisation. [1 mark] Question 1 continues on the next page Turn over ► box . Tellurium has several other isotopes. Two of these isotopes are 126Te and 124Te A different sample of tellurium is analysed using a TOF mass spectrometer. Which statement about kinetic energy (KE) is correct? Tick () one box. The KE of 126Te+ is greater than the KE of 124Te+ [1 mark] box The KE of 126Te+ is the same as the KE of 124Te+ The KE of 126Te+ is less than the KE of 124Te+ Turn over for the next question Turn over ► There are no questions printed on this page DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED box This question is about an experiment to determine the solubility of strontium hydroxide in water at 20 °C Strontium hydroxide is slightly soluble in water. Strontium hydroxide solution reacts in a similar way to calcium hydroxide solution. • Some solid strontium hydroxide is added to approximately 1 dm3 of distilled water in a stoppered flask. • The mixture is kept at 20 °C. Every day, the mixture is checked. If no solid is present in the flask, more solid strontium hydroxide is added. • On the day when no more solid needs to be added, the flask is opened and the mixture is filtered into another flask and stoppered. • A 25.0 cm3 sample of the filtrate is transferred to a conical flask with a pipette and a few drops of indicator added. • This sample is titrated with 0.100 mol dm–3 hydrochloric acid. • The titration is repeated several times with further samples of the filtrate. The results are shown in Table 1 on page 8. box . Suggest why the solution is kept until no more solid needs to be added. [1 mark] . Suggest why it is important to remove the undissolved strontium hydroxide before the titration. [1 mark] . After the filtration, the solution is stored in a stoppered flask. Suggest a reason for stoppering the flask. [1 mark] Question 2 continues on the next page *07* Turn over ► 0 2 . 4 The diagrams in Figure 2 show the part of a pipette with the graduation line. Which diagram identifies the pipette that is correctly filled? [1 mark] Tick () one box. Figure 2 A B C . Solubility can be quoted as ‘g of solute per 100 cm3 of solution’. Table 1 shows the results of the titrations between strontium hydroxide and hydrochloric acid. These can be used to determine the solubility of strontium hydroxide. Table 1 Titration Rough 1 2 3 Final burette reading / cm3 34.40 38.00 41.05 37.00 Initial burette reading / cm3 0.00 5.55 8.05 4.60 Titre / cm3 34.40 32.45 33.00 32.40 Give the equation for the reaction between strontium hydroxide and hydrochloric acid. Use the results in Table 1 to calculate the mean titre. Use the mean titre to calculate the solubility of strontium hydroxide, in g per 100 cm3 of solution, at 20 °C [6 marks]