OCR A Jun 2015 Paper 1 Q3

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This question is about Group 7 elements. (a) Chlorine can be made by the redox reaction below. MnO2(s) + 4HCl(aq) MnCl2(aq) + 2H2O(l) + Cl2(g) Using oxidation numbers, show what has been oxidised and what has been reduced in this reaction. OxidisedReduced[2] (b) Complete the electron configuration of a manganese atom. 1s2[1] (c) Chlorine gas can be added to a cold, dilute alkaline solution to form bleach. Write the equation for this reaction.[1] (d) A student bubbles chlorine gas through aqueous potassium iodide. A reaction takes place. (i) State what the student would observe.[1] (ii) Write the ionic equation for this reaction. Include state symbols.[1]OCR 2015<br />
 (e) Chlorine gas reacts with methane. One of the products is dichloromethane, CH2Cl2. (i) Chlorine is more electronegative than carbon and hydrogen, which have approximately equal electronegativity values. Explain what is meant by the term electronegativity.[2] (ii) Draw a 3-D diagram of a molecule of CH2Cl2. Use partial charges to indicate polar bonds. [2] (iii) Explain why a CH2Cl2 molecule is polar.[1] (f) Bromine has two isotopes, Br79 and Br81. The relative atomic mass of bromine is 79.9. Calculate the percentage of Br79 atoms in a sample of bromine.OCR 2015 Answer =% [1] [Total: 12] Turn over<br />

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