10 4 Sulfur is a bright yellow crystalline solid at room temperature. Sulfur forms rings of 8 sulfur atoms so the formula of the yellow solid is S8. (a) A section of a periodic table showing values of first ionisation energy in kJ mol–1 is shown. N 1400 P 1010 As 950 O 1310 S 1000 Se 940 F 1680 Cl 1250 Br 1140 (i) Which equation represents the first ionisation energy of sulfur? (1) A S(s) → S+(g) + e– B S8(s) → S8 +(g) + e– C S(g) → S+(g) + e– D S8(g) → S8 +(g) + e– (ii) Explain the trend in the values of the first ionisation energies for the group containing sulfur. 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Turn over 11 (iii) Explain why the first ionisation energy of sulfur is lower than that of chlorine. 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(iv) Explain why the first ionisation energy of sulfur is lower than that of phosphorus. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... 12 (b) Compound X is an oxide of sulfur. A gaseous sample of 0.318 g of X occupied a volume of 132 cm3 at a temperature of 420 K and pressure of 105 kPa. The number of moles of a gas and the volume occupied by it can be found using the ideal gas equation pV = nRT Calculate the relative molecular mass of X and hence its molecular formula. You must show all your working. [R = 8.31 J mol–1 K–1] (5) Turn over 13 (c) Sulfur and the other elements in Group 6 form dihydrogen compounds. Compound Atomic number of Group 6 element Melting temperature / K H2O 8 273 H2S 16 To be estimated H2Se 34 207 H2Te 52 224 H2Po 84 238 (i) Plot a graph of atomic number of the Group 6 element on the x-axis against melting temperature of the dihydrogen compound on the y-axis. (2) Melting temperature / K Atomic number 150 200 250 300 (ii) Give an estimate of the melting temperature of H2S. (1) .................................................................................................................................................................................................................................................................................... (Total for Question 4 = 16 marks)