EH0SCB

1

The University of Nottingham Ningbo, China

DIVISION OF ENGINEERING

A LEVEL 2 MODULE, AUTUMN SEMESTER 2009-2010

SCIENCE B - CHEMISTRY

Time allowed TWO HOURS

__________________________________________________________________________

Candidates may complete the front cover of the answer book and sign the attendance card

Candidates must NOT start writing their answers until told to do so

Answer ALL Questions

Only silent, self contained calculators with a Single-Line Display or Dual-Line Display are permitted in this examination.

Dictionaries are not allowed with one exception. Those whose first language is not English may use a

standard translation dictionary to translate between that language and English provided that neither language is the subject of this examination. Subject specific translation dictionaries are not permitted.

No electronic devices capable of storing and retrieving text, including electronic dictionaries and mobile phones,

may be used.

DO NOT turn examination paper over until instructed to do so

ADDITIONAL MATERIAL: Periodic Table, Standard Electrode Potentials and some constants are

attached to this exam paper at the back.

INFORNATION FOR INVIGILATORS: The paper needs to be collected at the end of exam.

EH0SCB

2

Resit Exam Science B – Chemistry August 2010 Section One: Multiple Choice Questions (Total 40 marks. 1 mark each)

1. Atoms of the same element with different mass numbers are called a. ions. b. neutrons. c. allotropes. d. chemical families. e. isotopes.

2. Which one of these species is an ion? a. B3+ b. NaCl c. He d. 14C e. none of these

3. An oxide ion, O2-, has: a. 8 protons and 10 electrons b. 10 protons and 8 electrons c. 8 protons and 9 electrons d. 8 protons and 7 electrons e. 10 protons and 7 electrons

4. The Stock system name for CrSO3 is a. chromium sulfide. b. chromium(II) sulfite. c. chromium(II) sulfate. d. chromium(III) sulfite. e. chromium sulfur oxide.

5. The total number of electrons present in a molecule of vanadium(III) chloride is a. 40. b. 57. c. 74. d. 86. e. 157.

6. The mineral manganosite is a compound of manganese-55 and oxygen-16. If 77% of the mass of manganosite is due to manganese, what is the empirical formula of manganosite? a. MnO b. Mn2O c. Mn2O2 d. MnO2 e. none of these

EH0SCB

3

7. What is the formula for the ionic compound formed by calcium ions and nitrate ions? a. Ca3N2 b. Ca(NO3)2 c. Ca2NO3 d. Ca2NO2 e. CaNO3

8. The correct name for NH4NO3 is a. ammonium nitrate. b. ammonium nitrogen trioxide. c. ammonia nitrogen oxide. d. hydrogen nitrogen oxide. e. hydrogen nitrate.

9. What is the average mass, in grams, of one atom of iron?

a. 6.02 1023 g

b. 1.66 10-24 g

c. 9.28 10-23 g d. 55.85 g

e. 55.85 10-23 g

10. An exothermic reaction causes the surroundings to a. warm up. b. become acidic. c. expand. d. decrease its temperature. e. release CO2.

11. Find the standard enthalpy of formation of ethylene, C2H4(g), given the following data: heat of

combustion of C2H4(g)= -1411 kJ/mol; 0fH [CO2(g)] = -393.5 kJ/mol; 0

fH [H2O(l)] = -285.8

kJ/mol. a. 52 kJ/mol b. 87 kJ/mol c. 731 kJ/mol

d. 1.41 103 kJ/mol

e. 2.77 103 kJ/mol

C2H4(g)+3O2(g)2CO2(g)+2H2O(l) , 2*(-393.5)+2*(-285.8)-(-1411)=52.4

12. Given H2(g) + (1/2)O2(g) H2O(l), H = -286 kJ/mol, determine the standard enthalpy

change for the reaction 2H2O(l) 2H2(g) + O2(g).

a. H = -286 kJ/mol

b. H = +286 kJ/mol

c. H = -572 kJ/mol

d. H = +572 kJ/mol

e. H = -143 kJ/mol

EH0SCB

4

13. Which of these compounds is most likely to be ionic? a. NCl3 b. BaCl2 c. CO d. SO2 e. SF4

14. Which of these ionic solids would have the largest lattice energy? a. NaCl b. NaF c. CaBr2 d. CsI e. CaCl2

15. The total number of lone pairs in NCl3 is a. 6. b. 8. c. 9. d. 10. e. 13.

16. The Lewis structure for a chlorate ion, ClO3-, should show ____ single bond(s), ____ double

bond(s), and ____ lone pair(s). a. 2, 1, 10 b. 3, 0, 9 c. 1, 2, 8 d. 3, 0, 10 e. 2, 1, 9

17. According to the VSEPR theory, the shape of the SO3 molecule is: a. pyramidal. b. tetrahedral. c. trigonal planar. d. distorted tetrahedron (seesaw). e. square planar.

18. The shape of the CS2 molecule is best described as: a. linear. b. trigonal planar. c. tetrahedral. d. bent. e. trigonal pyramidal.

EH0SCB

5

19. According to the VSEPR theory, the molecular shape of the carbonate ion, CO32 -, is:

a. square planar. b. tetrahedral. c. pyramidal. d. trigonal planar. e. octahedral.

20. The number of pi bonds in the oxalate ion (C2O42-) is:

a. 1. b. 2. c. 3. d. 4. e. 5.

21. What is the hybridization on the central atom in NO3- ?

a. sp b. sp2 c. sp3 d. sp3d e. sp3d2

22. The general formula for alkenes is: a. CnH2n+2 b. C2nH2n c. CnHn+2 d. CnH2n e. CnH2n-2

23. The two molecules represented below are examples of:

a. isomers b. isotopes c. alcohols d. carboxylic acids e. unsaturated hydrocarbons

24. Which of these is the systematic name for the compound represented below?

a. 2-ethylbutane b. 3-methylpentene c. 3-methyl-1-pentene d. 3-methyl-1-hexene e. 2-methylhexane

EH0SCB

6

25. Which is the product of the reaction of one mole of HCl with one mole of 1-butyne? a. 1-chloro-1-butene b. 1-chloro-2-butene c. 2-chloro-1-butene d. ethyl chloride + acetylene e. none of these

26. The reaction of an alcohol and a carboxylic acid yields: a. a hydrocarbon. b. an ester. c. an ether. d. an aldehyde. e. a ketone.

27. Oxidation of the 2-propanol will produce a/an: a. aldehyde. b. amine. c. alkene. d. ketone. e. carboxylic acid.

28. The reaction of Cl2 with CH4 to produce methyl chloride is an example of a/an: a. free radical reaction. b. addition reaction. c. reduction reaction. d. ester hydrolysis. e. polymerization.

29. Which of the following characteristics indicates the presence of weak intermolecular forces in a liquid? a. a low heat of vaporization b. a high critical temperature c. a low vapor pressure d. a high boiling point e. none of these

30. Helium atoms do not combine to form He2 molecules, yet He atoms do attract one another weakly through: a. dipole-dipole forces. b. ion-dipole forces. c. dispersion forces. d. dipole-induced dipole forces. e. hydrogen bonding.

EH0SCB

7

31. Which one of the following substances will have both dispersion forces and dipole-dipole forces? a. HCl b. BCl3 c. Br2 d. H2 e. CO2

32. For the chemical reaction system described by the diagram below, which statement is true?

If the Ea for the forward reaction is 25 kJ/mol and the enthalpy of reaction is -95 kJ/mol, what is Ea for the reverse reaction? a. 120 kJ/mol b. 70 kJ/mol c. 95 kJ/mol d. 25 kJ/mol e. -70 kJ/mol

33. The reaction A + 2B products has been found to have the rate law, rate = k[A] [B]2. While holding the concentration of A constant, the concentration of B is increased from x to 3x. Predict by what factor the rate of reaction increases. a. 3 b. 6 c. 9 d. 27 e. 30

34. The equilibrium constant expression for the reaction 2BrF5(g) Br2(g) + 5F2(g) is: a. Kc =[Br2] [F2]/[BrF5] b. Kc = [Br2] [F2]5/[BrF5]2 c. Kc = [Br2] [F2]2/[BrF5]5 d. Kc = [BrF5]2/[Br2][F2]5

e. Kc = 2[BrF5]2/([Br2] 5[F2]5)

35. Which of these situations will result if some CH4(g) is removed from the reaction

CO(g) + 3H2(g) CH4(g) + H2O(g) at equilibrium? a. H2O will be consumed. b. More CH4 and H2O will be produced. c. Kp will decrease. d. More CO will be produced. e. No change will occur.

EH0SCB

8

36. A negative sign for G indicates that, at constant T and P, a. the reaction is exothermic. b. the reaction is endothermic. c. the reaction is fast. d. the reaction is spontaneous.

e. S must be > 0.

37. Complete and balance the following redox equation:

MnO4- + H+ + Br- Mn2+ + Br2 + H2O (acidic solution)

The sum of the smallest whole-number coefficients is a. 6. b. 17. c. 21. d. 29. e. 43.

38. Given the following notation for an electrochemical cell Pt(s) | H2(g) | H+(aq) || Ag+(aq) | Ag(s), what is the balanced overall (net) cell reaction?

a. 2H+(aq) + 2Ag+(aq) H2(g) + 2Ag(s)

b. H2(g) + 2Ag(s) H+(aq) + 2Ag+(aq)

c. 2H+(aq) + 2Ag(s) H2(g) + 2Ag+(aq)

d. H2(g) + Ag+(aq) H+(aq) + Ag(s)

e. H2(g) + 2Ag+(aq) 2H+(aq) + 2Ag(s)

39. Calculate Ecell for a silver-aluminum cell in which the cell reaction is:

Al(s) + 3Ag+(aq) Al3+(aq) + 3Ag(s) a. -2.46 V b. 0.86 V c. -0.86 V d. 2.46 V e. none of these

40. Which one of the following reagents is capable of transforming Fe3+(1 M) to Fe2+(1 M)? a. H2(1 atm) b. NO3

- (1 M) c. O2(1 atm) d. Br- (1 M) e. H+(1 M)

EH0SCB

9

Section Two: True or False (Total 10 marks. 1 mark each)

41. The following reaction is spontaneous under standard state conditions at 25C:

AgCl(s) Ag+(aq) + Cl-(aq) (G = 55 kJ/mol) TRUE FALSE

42. The BrF5 molecule has polar bonds, and has a net dipole moment. TRUE FALSE

43. If the system 3H2(g) + N2(g) 2NH3(g) is at equilibrium, and more N2 is added, a net reaction that consumes some of the added N2 will occur until a new equilibrium is reached. TRUE FALSE

44. The hybridization of B in the BF3 molecule is sp3. TRUE FALSE

45. The oxidation product of 1-propanol when using Cr2O72- as the oxidizing agent is acetone.

TRUE FALSE

46. The rate law predicted by the following two-step mechanism is Rate = k[A][B].

TRUE FALSE

47. The rate constant of a first-order reaction, A products, can be determined from a graph of ln[A] versus t. TRUE FALSE

48. When an aqueous solution of NaCl is electrolyzed, Na(l) is produced at the cathode, and Cl2(g) is evolved at the anode. TRUE FALSE

49. Octane, C8H18, boils at 125C as compared to water, which boils at 100C. This information suggests that the dispersion forces in nonpolar octane molecules are stronger than dispersion forces and hydrogen bonding in water. TRUE FALSE

50. The oxidation number of N in NO is +7. TRUE FALSE

EH0SCB

10

Section Tree (Total 50 marks)

51. Complete following table. Don’t forget Roman numerals and Greek prefixes where appropriate. Remember that the proper capitalization is important! (6 marks)

Chemical Formula Systematic name Chemical Formula Systematic name

Fe2O3 (A) Iron (III) oxide NH4NO3 (B) Ammonium nitrate

CuCl2 (C) Copper (II) chloride H2S (D) Hydrogen sulfide

Mg(NO3)2 (E) Magnesium nitrate

(F)2,2-dimethylbutane

(G)Sn(NO2)2 tin (II) nitrite (H) NiSO4 nickel(II) sulfate

(I)N2O4 dinitrogen tetroxide (J) SiBr4 silicon tetrabromide

(K)

1,4-dimethylcyclohexane (L)

4-ethyl-2-hexene

52. The table below shows the fractions obtained from crude oil. Identify the boxes A-F (3 marks)

Name of fraction Number of carbon atoms Uses

Gases 1-4 bottled fuels for camping

Petrol (gasoline) (A) 4-12 fuel for cars

Naphtha 7-14 (B) petrochemicals

(C) Kerosene 11-15 jet fuel

Gas oil (diesel) (D) 15-19 central heating fuel

(E) Lubricating oil 20-30 lubrication

Fuel oil 30-40 (F) Fuel for ships

Wax 41-50 candles

Bitumen over 50 road surfacing

53. Complete the following table. (3 marks)

Species Hybridisation of

central atom Expected bond

angle Number(s) and type(s) of bonds around

central atom

CCl4 sp3 109.5 sigma bonds

CO2 (A) sp 180 2 sigma and 2 pi bonds

EH0SCB

11

NH3 (B) sp3 (C) 107.5 (D) sigma bonds

BCl3 (E) sp2 120 (F) sigma bonds

54. Explain Two of the following terms and give examples where appropriate to illustrate your definition. (Total 4 marks. 2 marks each)

A). Activation Energy

The minimum amount of energy required to initiate a chemical reaction.

B). Dipole-dipole

Forces that act between polar molecules. For example, HCl

C). Enthalpy change

The difference between the enthalpies of the products and the enthalpies of the reactants.

D). VSEPR

Valence-shell electron-pair repulsion. A model that accounts for the geometrical

arrangements of shared and unshared electron pairs around a central atom in terms

of the repulsive forces between electron pairs.

EH0SCB

12

55. Calculate Kc for the reaction 2HI(g) H2(g) + I2(g) given that the concentrations of each species at equilibrium are as follows: (4 marks) [HI] = 0.85 mol/L, [I2] = 0.60 mol/L, [H2] = 0.27 mol/L.

Kc= [H2][I2]/[HI]2= (0.60*0.27)/ (0.85*0.85)=0.22

56. Calculate the cell emf for the following reaction at 25C:

2Ag+(0.010 M) + H2(1 atm) 2Ag(s) + 2H+(pH = 6.0) (4 marks)

E=0.80-0=0.80V

57. Indicate all the types of intermolecular forces of attraction in HF(l). (2 marks)

Hydrogen bond, dipole-dipole force, dispersion force

58. Use the table of data shown below to calculate the average rate of the reaction A B between 10 s and 20 s. (4 marks)

Rate=ΔA/Δt=(0.050-0.10)/(20-10)=0.005 mol/l.s

59. What is the rate law that corresponds to the data shown for the reaction 2A + B C?

(4 marks)

R=258.26[B]2

60. If the cell emf of a Zn -Cu cell is 0.80 V when the concentration of Zn2+ is 2.0 M, what is the concentration of Cu2+? (5 marks)

Cu2++Zn->Cu+Zn2+

Half reactions and potentials

Cu2++2e->Cu Eo=0.34V

EH0SCB

13

Zn2++2e->Zn Eo=-0.76V

Eo=0.34-(-0.76)=1.10V

n=2, Q=[Zn2+]/[Cu2+],E=0.80, E0=1.10

0.80=1.10-0.0257/2ln(2.0/[Cu2+])

[Cu2+]=1.4Χ10-10M

61. The polymer poly(chloroethene), commonly known as poly(vinyl chloride) or PVC, can be produced as follows:

C C

H Cl

2 2 2

2

4 2 2 3

H H

H C C H Cl C H ClCHn

PVC

Step 1 Step 2 Step 3

Cl heat

(1) Using your knowledge of the reaction between bromine and ethene, name and outline a

mechanism for Step 1. (3 marks)

(2) Write an equation for Step 2 showing clearly the structure of the organic product. (1 mark)

(3) Draw the structure of the organic product of the reaction of C2H4Cl2 with an excess of warm

aqueous sodium hydroxide. (1 mark)

(4) Suggest why C2H3Cl, the organic product of Step 2, does not react with warm aqueous

sodium hydroxide. (1 mark)

(1) , electrophilic addition

(2) C2H4Cl2C2H3Cl+HCl

(3) alkoxy alcohol

(4) high electron density of double bond repels OH- or nucleophile

EH0SCB

14

62. Consider the reaction 2Fe3+(aq) + Fe(s) 3Fe2+(aq). Find the equilibrium constant for this

reaction at 25C. (5 mark)

Fe3++e->Fe2+ Eo=0.77V

Fe2++2e->Fe Eo=-0.44V

Eo=0.77-(-0.44)=1.21V

-RTlnK=-nFE0

lnK=nFEo/RT=2*96485*1.21/(8.314*298)=94.2

K=8.49X1040

------------------------------------ THE END ------------------------------------

EH0SCB

DATA SHEET

Physical constants

Avogadro constant

NA = 6.022 × 1023mol–1

Faraday constant

F = 96485 C mol–1

Gas constant

R = 8.314 J K–1mol–1= 0.08206 L atm K–1mol–1

Standard Reduction Potentials, E°

Reaction E°/V Reaction E°/V

Co3+(aq)+e–→Co2+(aq) +1.82 Fe3+(aq)+3e–→Fe(s) –0.04

Ce4+(aq)+e–→Ce3+(aq) +1.72 Pb2+(aq)+2e–→Pb(s) –0.13

MnO4–(aq) +8H+(aq) +5e–→Mn2+(aq) +4H2O +1.51 Sn2+(aq)+2e–→Sn(s) –0.14

Au3+(aq)+3e–→Au(s) +1.50 Ni2+(aq)+2e–→Ni(s) –0.24

Cl2+2e–→2Cl–(aq) +1.36 Cd2+(aq)+2e–→Cd(s) –0.40

O2+4H+(aq)+4e–→2H2O +1.23 Fe2+(aq)+2e–→Fe(s) –0.44

Pt2+(aq)+2e–→Pt(s) +1.18 Cr3+(aq)+3e–→Cr(s) –0.74

MnO2(s)+4H+(aq)+e–→Mn3++2H2O +0.96 Zn2+(aq)+2e–→Zn(s) –0.76

NO3–(aq)+4H+(aq)+3e–→NO(g)+2H2O +0.96 2H2O+2e–→H2(g)+2OH–(aq) –0.83

Pd2+(aq)+2e–→Pd(s) +0.92 Cr2+(aq)+2e–→Cr(s) –0.89

Ag+(aq)+e–→Ag(s) +0.80 Al3+(aq)+3e–→Al(s) –1.68

Fe3+(aq)+e–→Fe2+(aq) +0.77 Mg2+(aq)+2e–→Mg(s) –2.36

Cu+(aq)+e–→Cu(s) +0.53 Na+(aq)+e–→Na(s) –2.71

Cu2+(aq)+2e–→Cu(s) +0.34 Ca2+(aq)+2e–→Ca(s) –2.87

Sn4+(aq)+2e–→Sn2+(aq) +0.15 Li+(aq)+e–→Li(s) –3.04

2H+(aq)+2e–→H2(g) 0 (by definition)

EH0SCB

PERIODIC TABLE OF THE ELEMENTS