25 Answers for the HKCEE question are not provided 62 Topic 3 Metals 26 a

# 25 answers for the hkcee question are not provided 62

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25 Answers for the HKCEE question are not provided. 62 Topic 3 Metals 26 a) reduction b) 112 g c) 2Fe 2 O 3 + 3 C 4 Fe + 3 CO 2 d) Copper; Zinc 27 TiCl 4 (l) + 2H 2 O(l) TiO 2 (s) + 4HCl(aq) 165 g ? g Molar mass of TiCl 4 = (47.9 + 4 x 35.5) g mol –1 = 189.9 g mol –1 Number of moles of TiCl 4 = mass of TiCl 4 molar mass of TiCl 4 = 165 g 189.9 g mol –1 = 0.869 mol According to the equation, 1 mole of TiCl 4 can produce 1 mole of TiO 2 . number of moles of TiO 2 = 0.869 mol Molar mass of TiO 2 = (47.9 + 2 x 16.0) g mol –1 = 79.9 g mol –1 Mass of TiO 2 = number of moles of TiO 2 x molar mass of TiO 2 = 0.869 mol x 79.9 g mol –1 = 69.4 g the maximum mass of TiO 2 formed is 69.4 g. 28 a) 4FeS 2 (s) + 11O 2 (g) 2 Fe 2 O 3 ( s ) + 8 SO 2 ( g ) b) S(s) + O 2 (g) SO 2 (g) 1 tonne ? tonnes Molar mass of S = 32.1 g mol –1 Molar mass of SO 2 = (32.1 + 2 x 16.0) g mol –1 = 64.1 g mol –1 According to the equation, 1 mole of S can produce 1 mole of SO 2 . 32.1 g of S can produce 64.1 g of SO 2 . Mass of SO 2 = 1 tonne x 64.1 g 32.1 g = 2 tonnes the maximum mass of SO 2 that could be made is 2 tonnes. 63 Suggested Answers 29 CaO(s) + 3C(s) CaC 2 (s) + CO(g) ? g 128 g Molar mass of CaC 2 = (40.1 + 2 x 12.0) g mol –1 = 64.1 g mol –1 Number of moles of CaC 2 = mass of CaC 2 molar mass of CaC 2 = 128 g 64.1 g mol –1 = 2.00 mol According to the equation, 3 moles of C are required to make 1 mole of CaC 2 . number of moles of C required = 3 x 2.00 mol = 6.00 mol Mass of C required = number of moles of C x molar mass of C = 6.00 mol x 12.0 g mol –1 = 72.0 g 72.0 g of carbon are required. 30 2NaNO 3 (s) 2NaNO 2 (g) + O 2 (g) 1.70 g ? g Molar mass of NaNO 3 = (23.0 + 14.0 + 3 x 16.0) g mol –1 = 85.0 g mol –1 Number of moles of NaNO 3 = mass of NaNO 3 molar mass of NaNO 3 = 1.70 g 85.0 g mol –1 = 0.0200 mol According to the equation, 2 moles of NaNO 3 decompose to give 2 moles of NaNO 2 . number of moles of NaNO 2 = 0.0200 mol Molar mass of NaNO 2 = (23.0 + 14.0 + 2 x 16.0) g mol –1 = 69.0 g mol –1 Mass of NaNO 2 = number of moles of NaNO 2 x molar mass of NaNO 2 = 0.0200 mol x 69.0 g mol –1 = 1.38 g 1.38 g of sodium nitrate are formed. 64 Topic 3 Metals 31 a) Al 2 O 3 (s) + 3Mg(s) 3MgO(s) + 2Al(s) b) Al 2 O 3 (s) + 3Mg(s) 3MgO(s) + 2Al(s) ? g 16.2 g Molar mass of Al = 27.0 g mol –1 Molar mass of Al 2 O 3 = (2 x 27.0 + 3 x 16.0) g mol –1 = 102.0 g mol –1 Number of moles of Al = mass of Al molar mass of Al = 16.2 g 27.0 g mol –1 = 0.600 mol According to the equation, 1 mole of Al 2 O 3 is required to make 2 moles of Al. number of moles of Al 2 O 3 required = 0.600 2 mol = 0.300 mol Mass of Al 2 O 3 = number of moles of Al 2 O 3 x molar mass of Al 2 O 3 = 0.300 mol x 102.0 g mol –1 = 30.6 g 30.6 g of Al 2 O 3 are required. c) Al 2 O 3 (s) + 3Mg(s) 3MgO(s) + 2Al(s) 0.300 mol ? g According to the equation, 3 moles of Mg are required to react with 1 mole of Al 2 O 3 . number of moles of Mg required = 3 x 0.300 mol = 0.900 mol Mass of Mg = number of moles of Mg x molar mass of Mg = 0.900 mol x 24.3 g mol –1 = 21.9 g 21.9 g of magnesium are required. 32 a) According to the equation, 2 moles of NaN 3 can produce 3 moles of N 2 .  #### You've reached the end of your free preview.

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