AQA Specimen Paper 2 Q3

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Isooctane (C8H18) is the common name for the branched-chain hydrocarbon that burns smoothly in car engines. The skeletal formula of isooctane is shown in Figure 2. Figure 2 0 3 . 1 Give the IUPAC name for isooctane. . 2 0 3 Deduce the number of peaks in the 13C NMR spectrum of isooctane. [1 mark] [1 mark] Only one answer is allowed. Completely fill in the circle alongside the appropriate answer. WRONG METHODS CORRECT METHOD If you want to change your answer you must cross out your original answer as shown. If you wish to return to an answer previously crossed out, ring the answer you now wish to select as shown. Typesetter code Barcode<br /> Isooctane can be formed, together with propene and ethene, in a reaction in which one molecule of an alkane that contains 20 carbon atoms is cracked. Using molecular formulas, write an equation for this reaction. [1 mark] How do the products of the reaction in Question 3.3 show that the reaction is an example of thermal cracking? [1 mark] . 3 0 3 . 4 0 3 0 3 . 5 Deduce the number of monochloro isomers formed by isooctane. Draw the structure of the monochloro isomer that exists as a pair of optical isomers. [2 marks] Number of monochloro isomers Structure 0 3 . 6 An isomer of isooctane reacts with chlorine to form only one monochloro compound. Draw the skeletal formula of this monochloro compound. [1 mark] Question 3 continues on the next page Barcode Typesetter code Turn over <br /> 10 A sample of a monochlorooctane is obtained from a comet. The chlorine in the monochlorooctane contains the isotopes 35Cl and 37Cl in the ratio 1.5 : 1.0 Calculate the Mr of this monochlorooctane. [2 marks] Mr = Isooctane reacts with an excess of chlorine to form a mixture of chlorinated compounds. One of these compounds contains 24.6% carbon and 2.56% hydrogen by mass. Calculate the molecular formula of this compound. [3 marks] Molecular formula = . 7 0 3 . 8 0 3 Barcode Typesetter code<br /> 11 Turn over for the next question DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED Barcode Typesetter code Turn over <br />

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