AQA AS Specimen Paper 1 Q3

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. 1 0 3 Write an equation, including state symbols, for the reaction with enthalpy change equal to the standard enthalpy of formation for CF4(g). [1 mark] 0 3 0 3 . 2 Explain why CF4 has a bond angle of 109.5. [2 marks] . 3 Table 2 gives some values of standard enthalpies of formation (fH). Table 2 Substance F2(g) CF4(g) HF(g) fH / kJ mol1 680 269 The enthalpy change for the following reaction is 2889 kJ mol1. C2H6(g) + 7F2(g) 2CF4(g) + 6HF(g) Use this value and the standard enthalpies of formation in Table 2 to calculate the standard enthalpy of formation of C2H6(g). [3 marks] Standard enthalpy of formation of C2H6(g) = kJ mol1 Typesetter code Barcode<br /> Methane reacts violently with fluorine according to the following equation. CH4(g) + 4F2(g) CF4(g) + 4HF(g) H = 1904 kJ mol1 Some mean bond enthalpies are given in Table 3. Table 3 Bond Mean bond enthalpy / kJ mol1 CH 412 CF 484 HF 562 A student suggested that one reason for the high reactivity of fluorine is a weak FF bond . Is the student correct? Justify your answer with a calculation using these data. [4 marks] . 4 0 3 Turn over for the next question Barcode Typesetter code Turn over <br />

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