Set 12 Chemistry [Paper] 2

Page 1 of 6 SECTION A (60 Marks) Answer only three questions from this section . 1.(a) (i) Define the term colligative property . (01 mark) (ii)State the colligative properties of a solution. (02 marks) b) (i) Describe how molecular mass of cane sugar can be determine using one of the colligative properties. (06 marks) (ii)State limitations of the method used. (02 marks) c) The table below shows the freezing points of v arious solutions of cane sugar in solvent X. Mass of cane sugar (g /1000g of solvent X) 26 42 66 78 118 148 173 Freezing point. (oC) 5.11 4.87 4.51 4.33 3.73 3.28 2.91 (i) Plot a graph of freezing against mass of cane sugar and use graph to determine the: (03 marks) (ii) Freezing point of solvent X. (01 mark ) (iii)Freezing point constant for solvent X. (02 marks) [RMM of cane sugar = 342] d) State and explain how the freezing points of the solution would be affected if cane sugar associates in solution X. (03 marks) 2.(a) Define the terms : (@01 mark ) (i) Conductivity . (ii) Molar conductivity . b) The table below shows the molar conductivities of an aqueous solution of sodium hydroxide. Concentration (moldm-3) 0.01 0.04 0.09 0.16 0.25 0.36 Molar conductivity Λ/ Scm2mol-1 238 230 224 217 210 202 Page 2 of 6 (i) Plot a graph of molar conductivity against square root of concentration. (03½ marks) (ii) Use the graph to determi ne the molar conductivity of so dium hydroxide at infinity dilution. (01 mark) (iii)Explain the shape of the graph. (03 marks) c) Draw a sketch graph to show the change in the conductivity with volume of ammonia solution when 25cm3 of 0.1M methanoic acid is titrated with 0.1M ammonia solution. (02 marks) d) Expla in the …