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UNIVERSITY OF SWAZILAND

FINAL EXAMINATIONS 2016/2017

TITLE OF PAPER: INTRODUCTORY CHEMISTRY I

COURSE NUMBER: CHE1Sl

TIME ALLOWED: THREE (3) HOURS

INSTRUCTIONS:

• mERE ARE TWO SECTIONS: SECTION A AND SECTION B. ANSWER ALL THE QUESTIONS IN

SECTION A AND ANY TWO QUESTIONS FRQM SECTION B.

• SECTION A IS WORTH 50 MARKS AND EACH QUESTION IN SECTION B IS WORTH 25

MARKS.

• THE ANSWER SHEET FOR SECTION A IS ATTACHED TO mE QUESTION PAPER. DETATCH THE

ANSWER SHEET FROM THE QUESTION PAPER AND FILL IN ALL THE INFORMATION

REQUIRED

• For Sect ion A, record the letter corresponding to the correct answer on the Section A answer sheet which is attached

• AT THE END OF THE EXAM, BEFORE YOU LEAVE, PLACE mE ANSWER SHEET INSIDE THE

IJNISWA ANSWER BOOKLET CONTAINING YOUR ANSWERS TO SECTION B. DO NOT FORGET

---,--------------------- ­

A PERIODIC TABLE AND A TABLE OF CDNSTANTS HAVE BEEN PROVIDED WITH

THIS EXAMINATION PAPER.

PLEASE 00 NaT OPEN THIS PAPER UNTIL AUTIIORISED TO 00 SO BY THE

CHIEF INVIGILATOR.

1

SECTION A: ANSWER ALL THE QUESTIONS (50 MARKS)

1) What is the physical state in which matter has no specific shape but does have a specific volume? A) gas B) solid C) liquid D) salts E) ice

2) An element cannot ___ A) be part of a heterogeneous mixture B) be part of a homogeneous mixture C) be separated into other substances by chemical means D) interact with other elements to form compounds E) be a pure substance

3) Which of the following are chemical processes? 1. rusting of a nail 2. freezing of water 3. decomposition of water into hydrogen and oxygen gases 4. compression of oxygen gas A) 2,3,4 B) 1,3,4 C) 1,3 D) 1,2 E) 1,4

4) Osmium has a density of 22.6 g/cm3. What volume (in cm3) would be occupied by a 21.8 g sample of osmium? A) 0.965 B) 1.04 C)493

D) 2.03 x 10-3

E) 2.03 x 103

5) The number with the most significant zeros is ___ A) 0.00002510

B) 0.02500001 C) 250000001

D) 2.501 x 10-7

E) 2.5100000

2

6) If matter is uniform throughout and cannot be separated into other substances by physical processes, but can be decomposed into other substances by chemical processes, it is called a(n) ___ A) heterogeneous mixture B) element C) homogeneous mixture D) compound E) mixture of elements

7) A molecule of water contains hydrogen and oxygen in a 1:8 ratio by mass. This is a statement of

A) the law of multiple proportions B) the law of constant composition C) the law of conservation of mass D) the law of conservation of energy E) none of the above

8) In the absence of magnetic or electric fields, cathode rays ___' A) do not exist B) travel in straight lines C) cannot be detected D) become positively charged E) bend toward a light source

9) Which isotope has 45 neutrons? A) 80 Kr

36

B) ~~Br C) 78 Se

34

D) 34Cl 17

E) l03 Rh45

3

,­10) The element X has three naturally occurring isotopes. The masses (amu) and % abundances of the isotopes are given in the table below. The average atomic mass of the element is amu.

Isotope Abundance Mass 221X 74.22 220.9 220X 1278 220.0 218X 13.00 218.1

A) 219.7 B) 220.4 C) 220.42 D) 218.5 E) 221.0

11) An unknown element is found to have three naturally occurring isotopes with atomic masses of 35.9675 (0.337%),37.9627 (0.063%), and 39.9624 (99.600%), Which of the following is the unknown element? A)Ar B)K C) CI D)Ca E) None of the above could be the unknown element.

12) Which compounds do not have the same empirical formula? A) C2H2, C6H6

B) CO, C02

C) C2H 41 C3H6

D) C2H402, C6H1206

E) C2H5COOCH3, CH3CHO

13) Which species is an isotope of 39Cl?

A)40Ar+

B) 34s2­

C) 36Cl­

D) 80Br

E) 39Ar

14) The correct name for Al203 is ___'

A) aluminum oxide B) dialuminum oxide C) dialuminum trioxide D) aluminum hydroxide E) aluminum trioxide

4

15) Which of the following has eight valence electrons? A) Fe B) Kr C) Cl­D)N3­E) all of the a:bove

16) The Lewis structure of N2H2 shows ___

A) a nitrogen-nitrogen triple bond B) a nitrogen-nitrogen single bond C) each nitrogen has one nonbonding electron pair D) each nitrogen has two nonbonding electron pairs E) each hydrogen has one nonbonding electron pair

17) A valid Lewis structure of ___ cannot be drawn without violating the octet rule.

A) P043­

B) SiF4

C) CF4

D) SeF4

E) NF3

18) Of the possible bonds between carbon atoms (single, double, and triple), _....",-_ A) a triple bond is longer than a single bond B) a double bond is stronger than a triple bond C) a single bond is stronger than a triple bond D) a double bond is longer than a triple bond E) a single bond is stronger than a double bond

19) When the following equation is balanced, the coefficients are ___

A) 2,3,4,4 B) 1,4,8,9 C) 2,12,8,9 D) 4, 4, 32, 36 E) 2, 25, 16, 18

5

20) The formula weight of potassium dichromate (K2Cr207 ) is amu.

A) 107.09 B) 255.08 C) 242.18 D) 294.18 E) 333.08

. ,

21) Calculate the percentage by mass of lead in Pb(N03)2.

A) 38.6

B) 44.5 C) 62.6 D) 65.3 E) 71.2

22) How many atoms of nitrogen are in 10 g of NH4N03?

A) 3.5

B) 1.5 x 1023

C) 3.0 x 1023

D) 1.8

E) 2

23) There are ___ oxygen atoms in 30 molecules of C20H42S302.

A) 6.0 x 1023

B) 1.8 x 1025

C) 3.6 x 1025

D) 1.2 x 1024

E) 60

24) When the following equation is balanced, the coefficient of HCl is ___

CaC03 (s) + HCl (aq) --+ CaC12 (aq) + C02 (g) + H20 (1)

A)l B)2 C)3

D) 4 E) 0

6

25) Of the species below, only ___ is not an electrolyte. A)HCI

B) Rb2S04

qAr D)KOH E) NaCl

26) Which combination will produce a precipitate? A) Pb(N03)2 (aq) and HCI (aq)

B) Cu(N03)2 (aq) and KC2H302 (aq)

q KOH (aq) and HN03 (aq)

D) AgC2H302 (aq) and HC2H302 (aq)

E) NaOH (aq) and Sr(N03)2 (aq)

Answer: A Diff: 3 Var: 1 Page Ref: Sec. 4.2 LO: 4.2-4 GO: G2

27) Zinc is more active than cobalt and iron but less active than aluminum. Cobalt is more active than nickel but less active than iron. Which of the following conectly lists the elements in order of increasing activity? A) Co < Ni < Fe < Zn < Al B) Ni < Fe < Co < Zn < Al q Ni < Co < Fe < Zn < Al D) Fe < Ni < Co < Al < Zn E) Zn < Al < Co < Ni < Fe

28) What are the respective concentrations (M) of Mg2+ and C2H302- afforded by dissolving 0.600 mol

Mg(C2H302)2 in water and diluting to 135 mL?

A) 0.444 and 0.889 B) 0.0444 and 0.0889 q 0..889 and 0.444 D) 0.444 and 0.444 E) 4.44 and 8.89 Answer: E

29) Which of the following would require the largest volume of 0.100 M sodium hydroxide solution for neutralization? A) 10.0 mL of 0.0500 M phosphoric acid B) 20.0 mL of 0.0500 M nitric acid q 5.0 mL of 0.0100 M sulfuric acid D) 15.0 mL of 0.0500 M hydrobromic acid E) 10.0 mL of 0.0500 M perchloric acid·

7

30) is an oxidation-reduction reaction. A) Ice melting in a soft drink B) Table salt dissolving in water for cooking vegetables C) Rusting of iron D) The reaction of sodium chloride with lead nitrate to form lead chloride and sodium nitrate E) Neutralization of Hel by NaOH

31) Which one of the following is correct? A) v + A = c B) v A = c C) v = cA O)A cv E) vA = c

32) Which of the subshells below do DQ1 exist due to the constraints upon the angular momentum quantum number? A)2d B) 2s C)2p D) all of the above E) none of the above

33) Which quantum numbers must be the same for the orbitals that they designate to be degenerate in a many-electron system? A) n, 1, and ml

B) nonly C) n, 1, ml, and ms

D) msonly

E) n and 1only

34) Which one of the following configurations depicts an excited carbon atom?

A) 1s22s22p13s1

B) 1s22s22p3

C) 1s22s22p1

D) ls22s23s1

E) 1s22s22p2

8

\"

35) Which electron configuration repreSents a violation of Hund's rule for an atom in its ground state? A)

Is 2s

[!] [IT] B)

Is 25 2p

[ill [fi] C)

Is 25 2p

[TI [IT] It J, I I, D)

Is 2s 2p

[TI [IT] It I It I E)

Is 2s 2p

[TI [TI i i I i

36) The de Broglie wavelength of a 0.02900 gram bullet traveling at the speed of 647.4 mls is m.

A) 3.529 x 10-32

B) 3.529 x 10-33

C) 3.529 x 10-34

D) 3.529 x 10-35

E) 1.244 x 10-35

37) In which set of elements would all members be expected to have very similar chemical properties? A) 0, 5, Se B) N, 0, F C)Na, Mg, K D) 5, Se, 5i E) Ne, Na,Mg

38) Which isoelectronic series is correctly arranged in order of increasing radiusT

A)K+ < Ca2+ < Ar < CI­

B) Cl- < Ar < K+ < Ca2+

C) Ca2+ < Ar < K+ < Cl-

D) Ca2+ < K+ < Ar < Cl-

E) Ca2+ < K+ < CI- < Ar

9

39) In the second period of the periodic table, the atom with the highest first ionization energy is

A)Li B)N C)Ne D)Ar E) Be

40) Of the elements below, ___ is the most metallic. A) sodium B) barium C) magnesium D) calcium E) cesium

41) When two elements combine to form a compound, the greater the difference in metallic character between the two elements, the greater the likelihood that the compound will be ___ A) a gas at room temperature B) a solid at room temperature C) metallic D) nonmetallic E) a liquid at room temperature

42) The alkali metal that is naturally radioactive is ___ A) rubidium B) cesium C) lithium D) francium E) sodium

43) Most of the elements on the periodic table are ___ A) gases B) nonmetals C) metalloids D) liquids E) metals

44) Of the possible bonds between carbon atoms (single, double, and triple), ___ A) a triple bond is longer than a single bond B) a double bond is stronger than a triple bond C) a single bond is stronger than a triple bond D) a double bond is longer than a triple bond E) a single bond is stronger than a double bond

10

45) How many equivalent resonance forms can be drawn for C032-? (Carbon is the central atom.)

A) 1 B) 2

C)3 0)4 E) 0

46) The basis of the VSEPR model of molecular bonding is ___ A) regions of electron density on an atom will organize themselves so as to maximize s-character B) regions of electron density in the valence shell of an atom will arrange themselves so as to maximize overlap C) atomic orbitals of the bonding atoms must overlap for a bond to form 0) electron domains in the valence shell of an atom will arrange themselves so as to minimize repulsions E) hybrid orbitals will form as necessary to, as closely as possible, achieve spherical symmetry

47) In counting the electron domains around the central atom in VSEPR theory, a is not included. A) nonbonding pair of electrons B) single covalent bond C) core level electron pair 0) double covalent bond E) triple covalent bond

48) The electron-domain geometry of ___ is tetrahedral. A) CBq

B)PH3

C) CCl2BQ

0) XeF4

E) all of the above except XeF4

49) Of the following species, ___ will have bond angles of 120°.

A) PH3

B) CIF3

C) NCl3

0) BCl3

E) All of these will have bond angles of 120°.

50) The molecular geometry of the Br03- ion is ___

A) trigonal pyramidal B) trigonal planar C) bent 0) tetrahedral E) T-shaped

11

SECTION B: ANSWER ANY TWO QUESTIONS (25 MARKS EACH)

Question One

a) The width, length and height of a small box are 15.5,27.3 a.nd 5.4 cm, respectively. Calculate the volume of the box, using the correct number of significant figures in your answer. [2]

b) The average speed of a nitrogen molecule in air at 250 C is 515 m.s-l. Convert this to miles per hour.

[4]

c) Name the following compounds: i) ICIs ii) OF2 iii) Ca(CIO)2 iv) Cu(CI04)2

v) Fe203 [5]

d) Using the periodic table, predict the chemical formulas of the compounds formed by the following elements: i) Ga and F ii) Ca and H. iii) Mg and N iv) Al ~P ~

e) The structure of cyclohexane consists of six carbon atoms bonded to each other in a cyclic manner. The molecule contains twelve hydrogen atoms. Draw the structural formula of cyclohexane. [2]

f) How many of the indicated atoms are contained in one mole of each chemical formula:

i) Carbon atoms in C2HsCOOCH3 ii) oxygen atoms in Ca(CI04)2 iii) Hydrogen atoms in (NH4)2HP04

[3]. ­g) Give the chemical formula for each of the following binary molecular

substances:

i) Dinitrogen tetroxide ii) Sulphur hexafluoride iii) Tetraphosphorus hexasulphide

[3]

12

Question Two

a) Balance the following equations and indicate whether they are combination, decomposition, or combustion reactions:

i) C3H6(g) + 02(g) ----..~ C02(g) + H20(g) ii) NH4N03(S) ----.... N20(g) + H20(g)

[4]

b) Nicotine, a component of tobacco, is composed ofC, Hand N. A 5.250-mg sample of nicotine was combusted, producing 14.242 mg of CO2 and 4.083 mg of H20. Use the data to determine the empirical formula of nicotine. If nicotine has a molar mass of 160± 5 g/mol, what is its molecular, fo..rmula?

[10] c} Write balanced net ionic equations for the reactions that occur in each of the

following cases. Identify the spectator ion or ions in each case.

i) Cr2(S04)3(aq} + (NH4):.lC03(aq) )

ii) Fe(NOh(aq) + KOH(aq) )

[5]

d) Calcium carbide, CaC2, used to produce acetylene, C2H2, is prepared by heating calcium oxide, CaO, and carbon, C, to high temperature.

CaO(s} + 3C(s) ---~) CaC2(s} + CO(g)

If a mixture contains 8.49 kg of each reactant, how many grams of calcium carbide can be prepared?

[6]

13

Question Thee

a) For each element, indicate the number of valence electrons, core electrons, and unpaired electrons in the ground state. (il Silicon atom . (ii) Phosphorus

[4] b) Write a balanced equation for the reaction of cesium metal with

(i) Cb(g} [3]

c} Which neutral atom is isoelectronic with each of the following ions? i} 1-, ii) Z:r4+ [2]

.­d) Arrange the ionic compounds NaF, AlF3 and CaF2 in order of increasing lattice

energy. [3]

e) Consider a phosgene molecule, CbCO, where carbon is the central atom.

(i) Draw two non-equivalent Lewis structures for the molecule (ii) Using formal charges, determine which Lewis structure is the dominant

one [5]

f) Write the Lewis symbol for atoms of each of the following elements: (i) Al (ii) Ar

[4]

g) Nitric acid, HN03, is manufactured by the Oswald process, in which nitrogen dioxide, NOz, reacts

with water.

3NOz(g) + H20(g) ----)~ 2HN03(aq) + NO(g)

How many grams of nitrogen dioxide are required in this reaction to produce 8.60 g of nitric

acid? [4]

14

1

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9

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14

15

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19

20

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22

23

24

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CHE151/C201 Exam Section~nswer Sheet. Stud 10 No. Programme:

QuesNo. Letter corresponding to the correct answer QuesNo. Letter corresponding to the correct answer

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

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15

PERIODIC TABLE OF THE ELEMENTS

GROUPS 1 2 3 4 5 6 7 8 9

PERIODS IA IIA IIIB IVB VB via VIIB VIII

1.008

1 H 1

6.941 9.012

2 Li' Be 3 4

22.990 24.305

3 Na ~g TRANSITION ELEMENTS 11

39.0983 40.078 44.956 47.88 50.9415 4 K Ca Sc Ti V

19 20 21 22 23

85.468 87.62 88.906 91.224 92.9064

5. Rb Sr Y Zr Nb 37 38' 39 40 41

132.905 137.33 138.906 178.49 180.948

6 Cs Ba *La Hf Ta -.

55 56 57 '72 7:3. (223) 226.025 (227) (261 ) (262)

7 Fr Ra **Ac Rf Ha 87 88 89 104 105

51.996 54.938 55.847 58.933

Cr Mn Fe Co 24 25 . 26 27

95.94 98.907 101.07 102.906

Mo Tc Rll Rh 42 43 44 45..

- .

183.85 186.207 190.2 192.22

W Re Os Ir -.74., _ '7~ 76 ·77'

(263) . (262) (265) (266}

Uoh Uns Uno Une 106 107 108 109

10 11 12 13 14 15 16 17 18

IB liB iliA IVA VA VIA VilA VillA

4.003

He 2

10.811 12.011 14.007 15.999 18.998 20.180

B C N 0 F Ne 5 6 7 8 9 10

26.982 28.0855 30.9738 32.06 35.453 39.948

Ai Si P S Ci Ar 13 14 15 16 17 18

58.69 63.546 65.39 69.723 72.61 74.922 78.96 79.904 83.80

Ni Cll Zn Ga Ge As Se Br Kr 28 29 30 31 32 33 34 35 36

106.42 107.868 112.41 114.82 118.71 121.75 127.60 126.904 131.29

Pd Ag Cd In SA.­ . Sb T~ I Xe . 50-::

I46 47 . 48 49 51 52 53 54 I

_ d •• ,

.195.08 196.967 200.59 204.383 '201:.4 ~~ 208.980 pci (210) RriPt Au Hg 'fl. ·Pb.· 'Bl·.·· At 78 79 80 81 . '62.,;,' 83 84 85 86

... .. .. "; ..,­ - .~." '.... . '.' '.

, .~ .. - ..

.:>

• lanthanide series

•• Actinide series

140.115

Ce 58

140.908

Pr 59

144.24

Nd 60

(145)

Pm 61

150.36

Sm 62

151.96

Ell 63

157.25

Gd 64

158.925

Tb 65

162.50

Dy 66

164.930

Ho ' 67'

167.26

Er. 68

168.934

Tm 69

173.04

Yb 70

174.967

Lu 71

232.038

Th 90 -----­

231.036

Pa 91

238.029

U 92

237.048

~p (244)

Pll 94

(243)

Am 95

(247)

Cm 96

(241)

Bk 97

(251)

Cf 98

. (252)

Es 99

(257)

Fm 100

(258)

Md 101

(259)

No 102

(260)

Lr 103

Numbers below the symbol of the element indicates the atomic numbers. Atomic masses, above the symbol of the element, are based on the assigned relative atomic mass 01 12e ~ exactly 12: ( ) indicates the mass number 01 the isotope with the longest

half-lile.

SOURCE: International Union of Pure and Applied Chemistry, l. Mills. ed .• QlIalllilies, Unils. and Symbols ill Physical Chemistry. Blackwell Scientific Publications. Boston. 1988, pp 86-98.

4) ~

Fundamental Physical Constants (six significant figures)

Avogadro'snumber ' ;;y . Ni.".=;'6:02214X lOB/mol" • . , ..... J." """ .·..·.amu·. ·.·.·.-7"".··.·.·.'•. ·1. ·.'6'6.0''5'4.. X·.10·'-2.7.kgatoffilc massunlt ·., ..;i' .. . .

charge ofthee1ectt6Ji(0rProtonl e,:=cl:60218X 10-19 C FaradaycoflStant. P".";';.9;64853>Oo4C/mol

rmass of theeU:ctrori7ri~··{;~·.§.16939Xld7":Hkg j:mass of the neutron' .. ··mn·;-=L67493X'1O-27 kg F<

mass of the protonmp;'~r67262X 10.-27'kg i fPlanck's constant h' ..='6,626071<10-3: J-s . t

speed of lightina. vacuumc == 2"99792:><108 i:h/s f

standard acceleration of gravity .;==9.8()665.·rhls2. .

universal gas constant . ·":'.~~31~tj/(mol;Kt . .. L . . . .'. ' ... =,8:20578XJO~2 (atm'Ll/(mol-Kl 11'

,.. "·".:'v"",w't,.....·,,~"~~·.~~·'r.j"-1,'~-"~~·6~;, ..:=,->t ,t:,.""!; :~-'i:-;,ri"';.j_. ;!"'.~ ;-i;i;:~_~t.?~.~:.:: ,..:~;:·,.;;,+,~i~~::f~;r::--::·;~~,..,;.-'::·.:~,~,_·.J

Rydberg constant:-1.097 x 107 m-1

Conversions and Relationships

Length 'vol~e:;:St:: .'. r~ SI unit: meter, m 's{inut:ttibi{irit:ii~r, m) ...... ~~

l' dIll3;;"'lO~Jinj" .... f1 km = 1000 m = 0.62 mile (mil =lIiter (Ir· '., . J;:.

1 inch (in) = 2.54 em . =1.057quarts(qtl 'f;: 1 m == 1.094 yards (yd) 1 crn3 ·=:lmL·,: ..·· •l' 1 pm 10- 12 m = 0.01 A .c~~3.:;~~!~0~"~'\.~;.•..!~j~

Mass En~rii;:: .. SI unit: kilogram, kg ...SIunlt!j.6ule;:J<

1J. :~lkg-m2is~L; == 2.2051b . ':",,;lc6ulomb-volt(IC-V)

1 metric ton (tl 103 kg leal;: 4, lS,V···, ..... ;.. .

1 kg == 103 g

ro~t9J

TemperatUre .sIiutit:;kel~K

OK =~273.15°C .;: rnpofHiO :: O°C (273.15 K)

bp of H20 = 100°C (373.15 K) T (K) == T (0C) + 273.15 T (0C) == [T (OF) - 32H \ T (OF) == ~T (0C) + 32

'M mega­106

Pressure SI unit: pascal, Pa

1 Pa . = 1·N/m2

= 1 kg/m's2

1 atm = L01325XI05 Pa = 760 torr

1 bar = 1 X 105 Pa

'. Math relationships 'IT 3.1416

. volume of sphere = t'lTr3

volume of cylinder = 'lTr2h

, .~ " . ,'.