AS Level Chemistry A H032/02 Depth in chemistry

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Answer all the questions. 1 Bromine is a reactive element. It combines with other non-metals to form covalent compounds. Phosphorus tribromide, PBr3, and iodine monobromide, IBr, are examples of co... valent compounds used in organic synthesis. (a) PBr3 can be prepared by heating bromine with phosphorus, P4. (i) Write an equation for this reaction. …………………………………………………………………………………………. [1] (ii) How many molecules are present in 1.3535 g of PBr3? number of molecules = ……………………… [3] (iii) The ‘dot-and-cross’ diagram of a molecule of PBr3 is given below. Name the shape of this molecule and explain why the molecule has this shape. name: ……………………………………………………………………………………….. explanation: …………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. [3] Specimen 3 © OCR 2014 H032/02 Turn over (b) Bromine reacts with iodine to form iodine monobromide, IBr. The table below lists some average bond enthalpies which are required in different parts of this question. Bond Average bond enthalpy / kJ mol−1 Br–Br +193 I–I +151 I–Br +175 (i) Average bond enthalpy is the enthalpy change for the breaking of 1 mole of bonds in gaseous molecules. Why do Br2 and I2 not exist in the gaseous state under standard conditions? ……………………………………………………………………………………………… [Show More]

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