MI H2 Chem 2012 Prelim P1 Soln

2 Answer all questions on the OMR form provided (40 Marks) For each question, there are four possible answers, A, B, C and D. Choose the one you consider correct. 1 Zn reacts with VO3- ions to give Vn+. 3.9 g of Zn was required to react completely with 40.0 cm3 of 1.0 mol dm-3 of KVO3. What is the value of n? A 1 C 3 B 2 D 4 2 In which of the following pairs do the species have different shapes? A AlCl3 and CO32- B NH4+ and CH4 C NH3 and H3O+ D SeF4 and SO42- 3 The following graph shows how ionic radius changes across Period 3 for seven elements. A The sharp increase in ionic radius between the 4th and 5th element is due to an increase in the number of principal quantum shells. B There is a decrease in ionic radius for the first 4 elements in Period 3 due to decreasing shielding effect. C There is a decrease in ionic radius for the last 3 elements due to decreasing proton to electron ratio. D The first 4 elements form anions and hence have lower ionic radii than the last 3 elements which form cations. 11 12 13 14 15 16 17 Atomic Number Unknown PropertyIonic radius

[Turn over 3 4 In which of the following reactions is the acid acting as an oxidant? A KBr + H3PO4 ® HBr + KH2PO4 B MgO + H2SO4 ® MgSO4 + H2O C 12HClO4 + P4O10 ® 6Cl2O7 + 4H3PO4 D Cu + 4HNO3 ® Cu(NO3)2 + 2H2O + 2NO2 5 A 1dm3 flask containing helium at 2 kPa pressure is connected (at constant temperature) to a 2 dm3 flask containing neon at 1 kPa pressure. What is the final pressure after connection? A 4 3 kPa B 3 2 kPa C 5 3 kPa D 2 kPa 6 The use of the Data Booklet is relevant to this question. Phosphorus, P4, has the following molecular structure: P P P P Imagine that nitrogen were to form a similar molecule N 4 shown in the reaction below: 2N2(g) ® N4(g) What would be the value of ΔH (in kJ mol–1) for the above reaction? A 1028 B 1348 C 1954 D 2628

4 7 Which gas shows the greatest deviation from ideal gas behavior? A HCl B He C CH4 D N2 8 The use of the data booklet is relevant to this question. In many areas, tap water is slightly acidic due to dissolved carbon dioxide. Which metal will not be dissolved by tap water containing carbon dioxide? A Cr C Fe B Cu D Pb 9 Which of the following mixtures is not an acid/conjugate base pair? A H2O/OH- C NaH/Na B H2PO4-/HPO42- D NH3/NH2- 10 Which of the following pairs of solutions would form an acidic buffer when mixed? A HCN and NaCN B HNO3 and NaNO3 C NaOH and NaCl D HCl and NaOH 11 Bleaching solutions are manufactured by dissolving chlorine gas in sodium hydroxide solution to give the following reaction. Cl2 (g) + 2OH- (aq) OCl- (aq) + Cl- (aq) + H2O (l) Users are warned not to mix the bleach with other cleaning solutions to prevent evolution of hazardous chlorine gas. Which of the following actions will lead to liberation of chlorine gas? A Addition of water to bleach B Mixing of an alkali with bleach C Shaking bleach with table salt, NaCl D Subjecting bleach to high pressure

[Turn over 5 12 Given that, E quilibrium I: C (s) + O2 (g) CO2 (g) Kc1 = 3 Equilibrium II: C (s) + ½ O2 (g) CO (g) Kc2 = 2 Equilibrium III: CO (g) + ½ O2 (g) CO2 (g) Kc = ? What i s the numerical Kc value for the Equilibrium III? A 3 2 C 2 3 B 3 2 D 2 3 13 The rate of removal of the pain -killing drug paracetamol from the body is a first order reaction with a rate constant, k, of 0.26 h-1. How long will it take for 6.25% of the paracetamol ingested to remain in the body? A 2.7 hours C 8.1 hours B 10.6 hours D 13.5 hours 14 Sulfates of Group II metals exist as crystalline form as follows: MgSO4.7H2O CaSO4.2H2O SrSO4 BaSO4 Which one of the following accounts for this trend in hydration? A The atomic radius of the elements increases down the group. B The ionic character of these sulfates increases down the group. C The ionisation energy of the elements decreases down the group. D The radius of the cation increases down the group. 15 X is a mixture of two compounds. When X is treated with an excess of dilute hydrochloric acid, a colour gas is evolved and some, but not all of the mixture dissolves. Which one of the following mixtures could be X? A Ba(NO3)2 and Ca(OH)2 B Ag2SO4 and CaCO3 C CaCO3 and MgSO4 D Ca(OH)2 and MgCO3

6 16 A yellow precipitate of cadmium(II) sulfide is formed when H2S is passed into an aqueous solution of cadmium(II) ions, Cd2+. This precipitate is also obtained in the presence of dilute hydrochloric acid but not in the presence of concentrated hydrochloric acid nor in excess potassium chloride. Which explanation accounts for all these observations? A The presence of a high concentration of H+ (aq) suppresses the ionisation of H2S (aq). B The concentration of S2- (aq) is reduced by the formation of SCl42- (aq). C CdS (s) is insoluble in concentrated HCl (aq). D Cd2+ (aq) ions react with Cl- (aq) to form the complex ion [CdCl4]2- (aq). 17 A current of 2.0 A is used to plate Ni(s) from 500 cm3 of a 1.00 mol dm-3 Ni2+(aq) solution. What is the concentration of Ni2+(aq) after 3.0 hours? A 0.39 mol dm-3 B 0.46 mol dm-3 C 0.78 mol dm-3 D 0.89 mol dm-3 18 Which one of the following statements is correct about a reaction for which the equilibrium constant is independent of temperature? A The enthalpy change of reaction is zero. B Its rate constants do not vary with temperature. C There are equal numbers of moles of reactants and products. D The activation energies for both the forward and reverse reactions are zero.

[Turn over 7 19 Magnesium iodate (V) undergoes thermal decomposition to yield products as shown by the equation below. The other Group II iodates(V) also undergo similar thermal decomposition. 2Mg(IO3)2(s) ¾® 2MgO(s) + 2I2(g) + 5O2(g) The three graphs given below show the change in mass when 2.00 g each of three Group II iodates(V) are heated separately at a temperature T. Which three Group II iodates(V) give rise to these graphs? Graph (1) Graph (2) Graph (3) A Ca(IO3)2 Mg(IO3)2 Ba(IO3)2 B Mg(IO3)2 Ba(IO3)2 Sr(IO3)2 C Ca(IO3)2 Mg(IO3)2 Sr(IO3)2 D Sr(IO3)2 Ba(IO3)2 Ca(IO3)2 20 A compound X exhibits structural isomerism, the isomers being members of different homologous series. To which pair of isomers could X belong? A acyl chlorides and carboxylic acids B carboxylic acids and esters C amino acids and ammonium salts D amides and amino acids 21 What is the total number of structural and geometrical isomers for a compound with molecular formula C3H5F, excluding cyclic structures? A 3 B 4 C 5 D 6 0 mass/g time0 1.00 2.00 Graph (1) Graph (2) 2.00 1.00 0 time mass/g 0 2.00 1.00 0 time mass/g 0 Graph (3)Graph (1) Graph (2) Graph (3)

8 22 1,2-dibromo-3-chloropropane (DBCP) has been used in the control of earthworms in agricultural land. The structure of DBCP is shown below. C Br H H C Br H C Cl H H Which of the following reactions will lead to the highest yield of DBCP? A CH2=CHCH2Cl + Br2 / CCl4 ® DBCP B CH2=CHCHBr2 + HCl (g) ® DBCP C CH3CH2CH2Cl + 2Br2 / uv light ® DBCP + 2HBr D CH3CHBrCH2Br + BrCl / uv light ® DBCP + HCl 23 Compound J, C5H11Cl undergoes the following reaction. Ethanolic KOH C5H11Cl C5H10 Which of the following cannot be Compound J? A 1-chloropentane B 2-chloropentane C 2 –chloro-3-methylbutane D 1-chloro-2,2-dimethlypropane

[Turn over 9 24 A polypeptide was digested using two different enzymes. The fragments obtained were separated using electrophoresis. Anal