And pressure 1 12 n37962a01224 iv complete the

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Unformatted text preview: + 2HCl(.......... . . . . ) CaCl2(. . . . . . . . . . . . . . ) + H2O(l) + CO2(. . . . . . . . . . . . . . ) (v) Calculate the mass of 1 mol of calcium carbonate. [Assume relative atomic masses: Ca = 40, C = 12, O = 16.] (1) (vi) Use your data and the equation in (iv) to calculate the mass of calcium carbonate in the sample and the percentage by mass of calcium carbonate in the coral. Give your final answer to three significant figures. (2) (vii) When this experiment is repeated, the results are inconsistent. Suggest a reason for this other than errors in the procedure, measurements or calculations. (1) . . . . . . . . . . ............................... .............................................................. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................... .............................................................. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (Total for Question 16 = 12 marks) *N37962A01324* 13 Turn over 17 This question is about the element chlorine (atomic number = 17). (a) Complete the electronic structure of chlorine. (1) 1s2 2s2 . ....................... ............................................................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . (b) Chlorine forms compounds with magnesium and with carbon. (i) Draw a dot and cross diagram to show the electronic structure of the compound magnesium chloride (only the outer electrons need be shown). Include the charges present. (2) (ii) Draw a dot and cross diagram to show the electronic structure of the compound tetrachloromethane (only the outer electrons need be shown). (2) 14 *N37962A01424* *(iii) Suggest why the melting temperature of magnesium oxide is higher than that of magnesium chloride, even though both are almost 100% ionic. (3) . . . . . . . . . . ............................... .............................................................. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................... .................................................................
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