OCR A Jun 2013 Paper 2 Q3

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3 Compound I is found in biodiesel. It has the skeletal formula shown below. (a) Name the two functional groups that are present in a molecule of I.[2] (b) Why is compound I unsaturated?[1] (c) A sample of compound I is shaken with aqueous bromine. What colour change would you see? fromto[1] (d) Compound J is a stereoisomer of compound I. (i) What is meant by the term stereoisomers?[1] (ii) Draw or describe how the structure of J differs from that of I.[1]OCR 2013<br />
 (e) A student determined the enthalpy change of combustion for compound I. In her experiment, 1.34 g of compound I was used to heat 50.0 g of water. The temperature of the water changed from 20.2 C to 54.0 C. (i) What is meant by the term enthalpy change of combustion, Hc?[2] (ii) Calculate the energy released, in kJ, in the students experiment. The specific heat capacity of water is 4.18 J g1 K1. energy =kJ [2] (iii) The molecular formula of compound I is C17H32O2. Calculate the amount, in moles, of compound I used by the student. (iv) Calculate the enthalpy change of combustion of compound I. amount =mol [2]OCR 2013 Turn over Hc =kJ mol1 [3]<br />
 (v) The student noticed that compound I burnt with a yellow flame and produced black smoke. Suggest an explanation for these observations.[1] (f) Some scientists believe that we should use more biofuels such as biodiesel and bioethanol. Bioethanol is made by the fermentation of plant sugars such as glucose. Write the equation for the fermentation of glucose to make ethanol and state two essential conditions for this fermentation. equationessential conditions[3] [Total: 19]OCR 2013<br />

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