DHS H1 CHEM P1 ANS

Section A For each question, there ar e four possible answers A, B, C, and D. Choos e the one you consider to be correct. 1 When 10.0 cm3 of a 0.10 mol dm–3 solution of alkali metal salt MXO3 was reduced with an excess of acidifi ed potassium iodide solution, the resulting iodine required 60.0 cm 3 of 0.10 mol dm –3 sodium thiosulfate solution for its reduction. The anion could be reduced to A XO2 B XO2– C XO– D X– 2 The use of Data Booklet is relevant to this question. The successive ionization energies, in kJ mol –1, of an element X are given below. 870 1800 3000 3600 5800 7000 13200 What is X? A 33As B 53I C 8O D 52Te 3 Which of the following is a redox reaction? A AlH3 (g) + H– (g)  AlH4 – B Al3+ (aq) + 3OH– (aq)  Al(OH)3 (s) C 2 Al (s) + 3Cl2 (g)  2AlCl3 (s) D AlO2 – (aq) + H+ (aq) + H2O (l)  Al(OH)3 (s) [Turn Over 2

4 10 cm3 of a hydrocarbon was mixed with 100 cm 3 of oxygen gas which is in excess. The mixture was exploded and after it was cooled to room temperature, the residual gases occupied a volume of 80 cm 3. Upon passing the gases through potassium hy droxide, this volume decreased to 50 cm3. What is the formula of the unknown hydrocarbon? A C3H6 B C3H8 C C4H8 D C4H10 5 A sample of 0.025 mol of the chlori de of an element Z was dissolved in distilled water and the solution made up to 500cm 3. 12.5 cm 3 of this solution reacted with 25 cm 3 of 0.1 mol dm –3 silver nitrate solution. What is the most likely formula of the chloride? A Z2Cl B ZCl C ZCl2 D ZCl4 6 Consider the following four compounds: (I) (CH 3)3CH (II) CH3CH2CH2OH (III) CH3CH2CH2SH (IV) CH3CH2CH2CH3 What is the order of the increasing boiling point of the compounds? A I, IV, III, II B II, III, IV, I C III, II, IV, I D IV, I, II, III [Turn Over 3

7 AlCl3 reacts with LiAl H4 and (CH 3)3N to give (CH 3)3NAlH3. Which one of the following will be true of (CH3)3NAlH3? A The Al atom is tetrahedrally coordinated. B The Al atom is electron deficient. C It contains hydrogen bonding. D It is dimeric. 8 When 13.08g of zinc dust was added to 250 cm 3 of 1.0 mol dm –3 aqueous copper (II) sulfate, the temperature of the solution rose by 15C. The specific heat capacity of the final solution is 4.20 J g–1 K–1. Cu2+(aq) + Zn(s)  Zn2+(aq) + Cu(s) What is the enthalpy change for the above reaction? A -82.9 KJ mol–1 B -78.8 KJ mol–1 C -66.3 KJ mol–1 D -4.12 KJ mol–1 [Turn Over 4

9 Given the standard enthalpy change of c ombustion of but-1-ene and ethane are p and q KJ mol–1 respectively. What is the standard enthalpy change of the reaction 2C2H4(g)  C4H8(g)? C4H8 (g) 4CO2 (g) + 4H2O (l) 2C2H4 (g) + 6O2 (g) + 6O2 (g) A 2q – p KJ mol–1 B (p + q)/2 KJ mol–1 C q – 2p KJ mol–1 D (q – p)/2 KJ mol–1 10 The data below refers to the st andard molar enthalpy changes of combustion of some members of the alkanes. Alkane Hc /KJ mol–1 CH4 -890 C2H6 -1560 C3H8 -2220 C4H10 -2880 C5H12 -3510 C6H14 -4190 The enthalpy change of com bustion of another alkane X has a standard enthalpy change of combustion of -6780 KJ mol –1. The formula of X is likely to be A C 9H20 B C10H22 C C11H24 D C12H26 [Turn Over 5

11 The data below refers to the radii and charges of six ions. Ion P 2+ Q + R + T 2– U – V – Radius/nm 0.16 0.19 0.15 0.16 0.19 0.15 PT, QU and RV are ionic solids of the same lattice structure. Which one of the following gives the correct order of their la ttice energies with the lowest numerical value first? A QU PT RV B PT QU RV C PT RV QU D QU RV PT 12 In the presence of ultraviolet light, the “inert” xenon gas will react with fluorine gas to produce XeF 4 according to the equation, Xe (g) + 2 F2 (g) XeF4 (s) What is the correct equilibrium constant Kc? A B C D [Turn Over 6

13 Consider the following reaction scheme involving benzaldehyd e and ammonia in methanol to form an imine. CHO + NH3 NH + H2O Which of the following statement is true? A The rate of the forward reaction is faster than the backward reaction. B The forward reaction is favored by the addition of ammonia. C The backward reaction is favored by the addition of benzaldehyde. D The value of Kc increases with the addition of ammonia. 14 Which one of the following gives t he correct definition of an acid according to the Bronsted-Lowry theory? A It dissociates in water to give H+(aq) ions. B It is a proton donor. C It is a proton acceptor. D It is an electron donor. 15 What is the pH of the final soluti on formed by mixing equal volumes of two separate portions of dilute sulfuric acid of pH 2.0 and pH 4.0? A 2.3 B 2.6 C 3.0 D 3.6 [Turn Over 7

16 The decomposition of dinitrogen pentoxide N 2O5 was found to be first order with respect to the concentration of N 2O5. Which one of the following graphs confirms the results? A Rate of decomposition of N2O5 [N2O5] B Rate of decomposition of N2O5 [N2O5] C Rate of decomposition of N2O5 [N2O5] D Rate of decomposition of N2O5 [N2O5] [Turn Over 8

17 An energy diagram is shown below. What is the activation energy of the reverse reaction? A x B y C (x+y) D (y-x) x y 18 The reduction of a nitrile pr oduced a compound of formula C 3H7NH2. Which of the following wo uld be produced if the same nitrile was heated with hydrochloric acid? A CH3CONH2 B CH3CH2OH C CH3CH2COOH D (CH3)2CHCOOH [Turn Over 9

19 Serotonin is a monoamine neurotransmitter. N H NH2O H Serotonin How many sigma () and pi () bonds does serotonin have? A 26 and 2 B 26 and 4 C 28 and 2 D 28 and 4 20 Which one of the following, in alcoholic solution, produces a precipitate most rapidly when warmed with aqueous silver nitrate? A 1-chlorobutane B 1-bromobutane C 1-iodobutane D chlorobenzene [Turn Over 10

21 Consider the four compounds below: CH3CO2H CH 3CH2OH CH 2FCO2H CHF 2CO2H I II III IV Which of the following sequence a rrange the compounds in increasing pH for their aqueous solutions? A II, IV, III, I B IV, III, I, II C II, I, III, IV D I, III, IV, II 22 A student attempts to synthesis compound Z from the following synthetic route. Br2(l) Z What is compound Z that is formed in this reaction? A Br Br B Br Br C Br Br D Br Br