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SK017/2 Chemistry Paper 2 Semester I Session 2007/2008 (October 2007) 1.(a) Compound A consists of the element C, H and O. The complete combustionof 4.624g of the compound A yielded 6.557g of CO 2 and 4.026g of H 2 O.Determine the empirical formula of compound A.(b) The reaction between acetic acid, CH 3 COOH and barium hydroxide, Ba(OH) 2 produces a salt. Determine the maximum mass of the salt obtained if 17.13g of barium hydroxide is used.2.(a) Name the two transition elements that show anomaly in their electronicconfigurations. Write the electronic configuration and explain your answer.(b) The first six successive ionisation energies, IE, (MJ mol -1 ) of element B is asfollows:Based on the data given, determine the block and group for B. Explain your answer.3.(a) Draw the possible Lewis structures for COCl 2 and determine the more stablestructure. Explain your answer.(b) Predict the shape of IF 4+ ion.4.(a) i. Differentiate between end point and equivalence point in a titration.ii.Sketch a titration curve for the titration of 25.0 mL of 1.00 M NH 3 with 0.25 M HCl. Indicate the pH corresponding to the equivalence point.(b)Calculate the solubility in g L -1 for calcium fluoride, CaF 2 .[K sp CaF 2 = 3.2 x 10 -11 ]5.(a) State Charles`s law. Explain Charles`s law from a kinetic perspective.A piston-cylinder holds 7.00 g of CO 2 at 160 o C and 110 kPa. How manygrams of CO 2 will it hold at 27 o C under the same pressure?(b) When a solid is heated in a closed container, it undergoes phase changes.Describe the process.IE 1 IE 2 IE 3 IE 4 IE 5 IE 6 1.402.864.587.489.4456.27 6.(a) State the success and failure of Bohr`s atomic model.Calculate the wavelength for a spectral line produced when an electron fallsfrom n = 5 to n = 3. Name the series and state the region of electromagnetic spectrumfor the line.(b) Describe the acid-base character of oxides of elements in period 3. For eachtype of oxide, give one example and write a balanced chemical reaction that showstheir acid-base character.7.What is meant by hybridisation?Glycine, NH 2 CH 2 COOH is one of the essential amino acids. State the types of hybridisation of C, N and O atoms in the glycine molecule. Draw and label theoverlapping of orbitals showing all the σ and Π bonds formed in the glycinemolecule.Predict the C-N-H and C-C-O angles in the glycine molecule. Explain your answer.8.(a) Two moles of hydrogen bromide, HBr, is placed in a 4 L container. At hightemperature, it decomposes according to the following equation: 2HBr(g) H 2 (g) + Br 2 (g)At equilibrium, the concentration of bromine is 0.1 M. Calculate theequilibrium constant, K c and the percentage of dissociation of HBr.(b)Carbon monoxide reacts with oxygen to produce carbon dioxide as follows:2CO(g) + O 2 (g) 2CO 2 (g) , H = - 514 kJExplain how the amount of CO 2 could be increased.9.(a) What is an indicator?The properties of some common indicators are given in TABLE 1 . Choosethe best indicator for detecting the equivalence point of a titration of a week acid anda strong base. Explain your answer. TABLE 1 IndicatorpK a Effective colour range pHColour in acidformColour in baseformMethyl orange4.23.1 – 4.4RedYellowBromothymol blue7.16.0 – 7.8YellowBlueThymol blue8.27.9 – 9.4YellowBluePhenolphthalein 9.58.3 – 10ColourlessRed ∆ (b)A 25.00 mL of 0.50 M acetic acid, CH 3 COOH solution is titrated with 0.50 Msodium hydroxide, NaOH solution. Calculate the initial pH of the acid solution.Qualitatively, predict the pH of the solution after the addition of 25.00 mL NaOH solution. Explain your answer.[K a (CH 3 COOH) = 1.8 x 10 -5 ]10.(a) TABLE 2 shows phase equilibrium data for substance D . TABLE 2 Pressure (atm)Temperature ( o C)Sublimation point2.5- 80Triple point5.0- 60Critical point40.030Melting point 115.0- 30Melting point 235.0- 15Boiling point 120.010Boiling point 230.025Plot and label a phase diagram for D .Does D sublime at 20 atm? Explain your answer.(b)Ethanol, C 2 H 5 OH and methanol, CH 3 OH form an ideal solution. The vapour pressures of pure ethanol and pure methanol are 6.5 kPa and 10.3 kPa,respectively at 25 o C. Calculate the vapour pressure of a solution made from30 g of ethanol and 20 g of methanol at 25 o C.[C 2 H 5 OH = 46; CH 3 OH = 32]
