Ii determine the molecular formula of crocetin given

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(ii) Determine the molecular formula of crocetin given that 0.300 mole of crocetin has a mass of 98.5 g 78. A solution containing ammonia requires 25.0 cm 3 of 0.100 mol dm 3 hydrochloric acid to reach the equivalence point of a titration. (i) Write an equation for the reaction of ammonia with hydrochloric acid (1) (ii) Calculate the amount (in mol) of hydrochloric acid and ammonia that react. (2) (iii) Calculate the mass of ammonia in the solution. (2) 79. A toxic gas, A, consists of 53.8% nitrogen and 46.2% carbon by mass. At 273 K and 1.01×10 5 Pa, 1.048 g of A occupies 462 cm 3 . Determine the empirical formula of A. Calculate the molar mass of the compound and determine its molecular structure. 80. 100 cm 3 of ethene, C 2 H 4 , is burned in 400 cm 3 of oxygen, producing carbon dioxide and some liquid water. Some oxygen remains unreacted. (a) Write the equation for the complete combustion of ethene. (b) Calculate the volume of carbon dioxide produced and the volume of oxygen remaining. 81. (a) Write an equation for the formation of zinc iodide from zinc and iodine. (b) 100.0 g of zinc is allowed to react with 100.0 g of iodine producing zinc iodide. Calculate the amount (in moles) of zinc and iodine, and hence determine which reactant is in excess. (c) Calculate the mass of zinc iodide that will be produced. 82. An oxide of copper was reduced in a stream of hydrogen as shown below.
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11 hydrogen gas HEAT oxide of copper in a dish excess hydrogen burning After heating, the stream of hydrogen gas was maintained until the apparatus had cooled. The following results were obtained. Mass of empty dish = 13.80 g Mass of dish and contents before heating = 21.75 g Mass of dish and contents after heating and leaving to cool = 20.15 g 83. Copper metal may be produced by the reaction of copper(I) oxide and copper(I) sulfide according to the below equation. 2Cu 2 O + Cu 2 S 6Cu + SO 2 A mixture of 10.0 kg of copper(I) oxide and 5.00 kg of copper(I) sulfide was heated until no further reaction occurred. (a) Determine the limiting reagent in this reaction, showing your working. (b) Calculate the maximum mass of copper that could be obtained from these masses of reactants. 84. The reaction below represents the reduction of iron ore to produce iron. 2Fe 2 O 3 + 3C 4Fe + 3CO 2 A mixture of 30 kg of Fe 2 O 3 and 5.0 kg of C was heated until no further reaction occurred. Calculate the maximum mass of iron that can be obtained from these masses of reactants.
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  • Winter '13
  • Smith
  • Mole, mol, ECF, mol dm–3

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