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CONFIDENTIAL EH/OCT 2007/CPE435

UNIVERSITI TEKNOLOGI MARAFINAL EXAMINATION

COURSECOURSE CODEEXAMINATIONTIME

: PROCESS CHEMISTRY: CPE435: OCTO BER 2007: 3 HOURS

INSTRUCTIONS TO CANDIDATES1. This que stion paper consists of SIX (6) questions.

Answer FOUR (4) questions only in the Answer Booklet. Start each answer on a new page..3.

4.

Do not bring any material into the examination room unless permission is given by theinvigilator.Please ensure that this examination pack consists of:

i) the Que stion Paperii) a one - page Append ixiii) an Ans we r Booklet - p rovided by the Faculty

DO NOT TURNT ISP GEUNTILYOU RE TOLD TO DO SOThis examination paper consists of 7 printed pages Hak Cipta Universiti Tekn ologi MARA CONFIDENTIAL

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CONFIDENTIAL 2 EH/OCT 2007/CPE435

QUESTION1a) State Le Chatelier's Principle.

(1 mark)b) Consider the following reaction:

C 2 S ) H 2 g ) - H 2 g ) C 0 9 ) A H = +4 0 1 8 kJ m01"1Explain withareason what the effect of the following are on the position of equilibrium:i) An increase in tempe rature

(2 marks)ii) Adecrease in pressure (2 marks)iii) Increasing the amo unt of carbon monoxide present (2 marks)iv) The addition of a catalyst (2 marks)

c) Consider the following reaction:3F e (s ) + 4 H 2O (g ) - Fe3O4(s) +4H2(g)

The equilibrium pressure constant, K p, for the above reaction is 3.89* 10"6at 2 5C.i) Write and calculateKc.

(2 marks)ii) If the equilibrium water vapour concentration is 1.93 * 10'3M. Calculatetheequilibrium hydrogen gas concentration and its partial pressure. (3 marks)iii) Calculate the total pressure exerted by the system.

(2 marks)d) Write theconce ntration equilibrium constant ex pression for thereaction presentedin1(b). (1 m ark)

Evaluate the effectsof the followingon thepositionof equilibrium with respectto thereaction quotient,Q:i) If there is no initial carbon mon oxide (1 mark)

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i i) The initial carbo n dioxide concentration is greater than the equilibrium con centration(1 mark)e) A1.5 L flask heldat597C is filled with 1.3 m oles an d 3.4 mo lesofhydrogen and iodinegas, respectively, which react to form hydrogen iodide.Kc for the systematequ ilibriumis 7.20. Calculate theequilibrium concentrations of hydrogen, iodine andhydrogeniodide.

2HI(g )(6 marks)

QUESTION2a) Balan ce the fol lowin g redox react ions indicat ing wh at has been ox idised and reduce dbywri t ing the corre spo ndin g ox idat ion s tates of the reduc ed and ox idised spec ies:

Acidic condi t ionsi) MnO 2 (s ) -> MnO

ii) Fe ;a+q) + Bi(3a+q) -> NaBiO 3(aq)+ Fe(2a+q)(3 marks)

(3 marks)i i i) MnO; ( a q )+C O 2 ( g ) -> Mn(2a+q)+C 2 O j a q ) (3 marks)Basic condi t ionsiv) io ^ +v o ( 2 a + q ) -> vo; ( aq ) + i2(s) (4 marks)v) Afc> + MnO 2(aq) ' (4 marks)

b) W hat type of redo x reaction is taking place in 2(a)(i)? (1 mark)c) Wh ich of the following solutions produces the most ions?0 .29 MHC I 1 0MC H 3 C O 2 H 0.21 M Ba(OH)2 (2 marks)d) Calculate the pH for the three solutions in (c), whereKa for ethanoic acidis1.75*10~5.(5 marks)

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QUESTION 3a) W rite the conjugate bases for each of the following acids:

HCIO 4; H2S, P H 4 \ and HCO3"?b) W rite the conjugate acids for each of the following bases:

CN",SO42", H2O and HCO3"?

c) Calculate the concentration of O H '(aq) in a solution at 25C in which -

(4 marks)

(4 marks)

ii) [H+] =iii) [H+] = 1 00x [OH" ]Indicate whethe r the solution is acidic, basic or neutral. (6 marks)

d) Calculate the concentration of OH" in a 0.15 M solution of NH 3, which has aKbvalueof 1.8 X10"5. (5 marks)e) Calculate the base-dissociation constant, Kb, for the conjugate base of the weak acidHF,which has aKavalue of 6.8 x 10"4. (2 marks)f) Calculate the acid-dissociation constant,Ka, for the conjugate acid of NH 3, which hasaKbvalue of 1 .8x1 0"5 . (2 marks)g) Explain whe ther pure water is a good conductor of electricity? (2 marks)

QUESTION 4a) A voltaic cell is based on the following two standard half-reactions:

Cd2+ (aq) + 2e -> Cd(s) Ered(C d27Cd) = -0.403 VSn2+ (ag) + 2e" -> Sn(s) Eed(S n2+ /Sn) = -0.1 36 V

Using the given standard reduction potentials for the two half-reactions, determinethe half-reactions that occur at the cathode and the anode, and the standard cellpotential. (4 marks) Hak Cipta Universiti Teknologi MARA CONFIDENTIAL

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b) Verify wh ethe r the following reactions arespontaneous under s tandard conditionsusing the stand ard reduction potentials given.

i) Cu(s) + 2H+(aq) ->C u2+(ag)+H2(g) ECu 2+= +0.34V

ii) CI2(g) + 2r(aq ) -> 2Cr(aq)+I2(s) Eed(C I2/Cr)=+ 1 . 3 6 VEed(l2/r)=+ 0 . 5 4 V (5 marks)c) Ifthe voltageofaZn-H + cellis0.45V at25C wh en EZn 2+=-0.76 V, [Zn2+ ]= 1.0 Mand PH2 =1 . 0 atm, what is the concentrationofH+? (5 marks)d) Write the half-reactions that occurat a hydrogen electrode when it servesas thecathode and w henitserves as the anode of a voltaic cell. (2 marks)e) Wh at isstandard about the standard hydrogen electrode? (2 marks)f) What is the role of the Pt foil in a standard hydrogen electrode? (3 marks)g) Sketch a standard hydrogen electrode. (4 marks)

QUESTION5a) Consider the following reaction:

CH 3OHfoj -> CO(g) + 2H2(g ) AH =+90 .7kJi) Is this reaction exothermic or endothermic?

(2 marks)ii) Calculate the amount of heat transferred when 1.60kg of CH3OH(g) isdecomposed according to this reaction at constant pressure. (3 marks)b) Naphthalene (Ci0H 8) is asolid arom atic comp ound often soldasmo thballs.Thecomplete combustion of this sub stance yields CO2(g ) andH2O(7)at 25Candreleases 51 54 kJ/mol.

i) Write balanced equations for the formationofnaphthalene from its elements andfor its combustion.(6 marks) Hak Cipta Universiti Te knologi MARA CONFIDENTIAL

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i i) Calculate the standard enthalpy of formation of nap hthalene. (4 marks)c) The standard enthalpies of formation of gaseous propyne (C3H 4), propylene (C 3H6),and propane (C 3H8) are +185.4, +20.4 and -103.8 kJ/mol respectively.

i) Calculate the heat evolved per mole on comb ustionofeach substancetoyieldCO2(g ) and H2O(g). (3 marks)ii) Calculate the heat evolved on combustionof kg of each substance. (3 marks)iii) Which is the most efficient fuel in terms of heat evolved per unit mass? (4 marks)

QUESTION6a) The reaction between ethyl bromide (C2H5Br) and hydroxide ionsinethyl alcoholat330K proceeds as follows:

C 2H 5Brfa/c; +OH (alc) - C2H5OH(7)+ Bf(alc)The reaction is first order with respect to ethyl bromide and h ydroxide ions. The rateof disappearanceof ethyl bromideis 1.7 x10*7M/s when [C 2H 5Br]is0.0477 Man d[OH ] is 0.100M,i) Write the rate law and calculate the rate constant with the correct units. (3 marks)ii) How wo uld therateofdisappearance ofethyl brom ide ch ange if the solutionwere diluted by adding an equal volume of pure ethyl alcohol to the solution?(3 marks)

b) i) The gas-pha se decompo sit ionofSO 2CI2 proceeds according to:SO 2CI2(g) - SO 2(g )+CI2(g)

and is first order with respect to SO 2CI2 . At 600 K the ha lf life for this reactionis2.3x1 0 5s. W hat is the rate constant at this temp eratu re? (3 marks)ii) At 320C the rate constant is 2.2 x 105 s 1. What is the half-life at thistemperature? (3 marks)

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c)

d)

Name the following compounds:i)

CH, (2 marks)ii) CH3I~Cri2 CH2C HCH2 CH3

H H(2 marks)

Draw the condensed structures of the esters formed in the following reactions andname the final compound in each case.i) Butanoic acid and methanol

ii) Benzoic acid and 2-propanol

iii) Propanoic acid and dimethylamine.

(3 marks)

(3 marks)

(3 marks)

END OF QUESTION PAPER

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CONFIDENTIAL APPENDIX 1 EH/OCT 2007/CPE435

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