OCR A Jan 2009 Paper 1 Q1

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Answer all the questions. 1 Carbon occurs in a wide range of compounds and is essential to living systems. (a) Two isotopes of carbon are 12C and 13C. (i) State what is meant by the term isotopes.[1] (ii) Isotopes of carbon have the same chemical properties. Explain why.[1] (iii) The 12C isotope is used as the standard measurement of relative masses. Define the term relative isotopic mass.[2]OCR 2009<br />
 (b) One form of naturally occurring carbon is graphite. The table below lists some properties of graphite. electrical conductivity good conductor hardness melting point soft very highDescribe the bonding and structure in graphite. Explain, in terms of bonding and structure, the properties of graphite shown above. In your answer, you should use appropriate technical terms, spelt correctly.[5]OCR 2009 Turn over<br />
 (c) In the sixteenth century, a large deposit of graphite was discovered in the Lake District. People at the time thought that the graphite was a form of lead. Nowadays, graphite is used in pencils but it is still referred to as pencil lead. A student decided to investigate the number of carbon atoms in a pencil lead. He found that the mass of the pencil lead was 0.321 g. (i) Calculate the amount, in mol, of carbon atoms in the students pencil lead. Assume that the pencil lead is pure graphite. (ii) Using the Avogadro constant, NA, calculate the number of carbon atoms in the students pencil lead. answer =mol [1] number of carbon atoms =[1] [Total: 11]OCR 2009<br />

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