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GNC501S - GENERAL CHEMISTRY 1A - 2ND OPP - JULY 2023 |
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nAm I BI A un IVERS ITY
0 F SCIEn CE An D TECH n 0 LOGY
FACULTYOF HEALTH,NATURALRESOURCEASND APPLIEDSCIENCES
DEPARTMENTOF BIOLOGYC, HEMISTRYAND PHYSICS
QUALIFICATIONB:ACHELOROF SCIENCE
QUALIFICATIONCODE:07BOSC
LEVEL5:
COURSECODE:GNCS0lS
COURSENAME:GENERALCHEMISTRY lA
SESSIONJ:ULY 2023
PAPERT: HEORY
DURATION:3 HOURS
MARKS:100
SECOND/SUPPLEMENTAORYPPORTUNITYEXAMINATIONQUESTIONPAPER
EXAMINER(S) MRS. LEONORITHA R. NAOMAS
MODERATOR: DR. MARIUS MUTORWA
INSTRUCTIONS
1. Answer ALL the questions.
2. Write clearly and neatly.
3. Number the answers clearly
4. All written work must be done in blue or black ink and
sketches can be done in pencil
5. No books, notes and other additional aids are allowed
PERMISSABLMEATERIALS
Non-programmable calculators
ATTACHMENTS
1. List of useful constants
2. Periodic Table
THISQUESTIONPAPERCONSISTSOF9 PAGES
(Including this front page, list of useful constants and Periodic Table)
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SECTIONA: MULTIPLECHOICEQUESTIONS
[60]
• There are 20 multiple choice questions in this section. Each question carries 3 marks.
• Answer ALL questions by selecting the letter of the correct answer.
• Choose the best possible answer for each question, even if you think there is another
possible answer that is not given.
1. Which of the following pairs of species is not a conjugate acid-base pair?
A. HCI and W
B. HSO4-and SO/-
C. · H2SO4and HSO4-
D. H2Oand OW
2. Which of the following reactions illustrate Al(OHh acting as a Lewis acid?
A. Al(OH)3 Al3+ + 30W
B. Al(OHh + OW Al(OH)io- + H2O
C. Al(OHh
Al(OH)4-
D. Al(OHh + 3W Al3+ + 3H2O
3. Calculate the hydroxide ion concentration of a solution if its pH is 6.389.
A. 1.00 X 1011-14 mol/L
B. 4.08 x 1011- 7 mol/L
C. 9.92 x 1011-7 mol/L
D. 2.45 x 1011-8 mol/L
4. Consider each of the following pairs of acids. Which statement is correct?
A. CIO2is a stronger acid than HCJO4.
B. H2SO4is a stronger acid than H2SeO4.
C. H2Ois a stronger acid than HF.
D. H2Sis a stronger acid than H2Se.
5. According to Bohr Theory, which of the following transitions in the hydrogen atom will
give rise to the least energetic photon? Use the equation: En= (-2.18 x 1011-18 J)(l/n2)
A. n = 5 ton= 3
B. n = 6 ton= 1
C. n = 4 ton= 3
D. n = 6 ton= 5
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6. Which of the following elements has the largest ionization energy?
A. Na
B. Ne
C. F
D. K
7. In Bohr's model of the hydrogen atom, the radius of an orbit
A. is proportional to n2.
B. is smallest for the highest energy state.
C. increases when a photon of light is emitted from an excited atom.
D. can have any value that is larger than the ground-state radius.
8. Which of the following statements about periodic properties is incorrect?
A. Both electron affinity and ionization energy decrease down a group.
B. Atomic size increases to the right across a period.
C. Ionization energy increases to the right across a period.
D. Atomic size increases down a group.
9. Deviations from the ideal gas law are less at:
A. high temperatures and high pressures
B. high temperatures and low pressures
C. low temperatures and high pressures
D. low temperatures and low pressures
10. Determine the number of moles of aluminum in 2.154 x 10"-1 kg of Al.
A. 5816 mol
B. 7.984 mol
C. 6.02 x 10"23 mol
D. 4.801 mol
11. This equation is unbalanced: PCl3 + H2O
the coefficients are, respectively:
A. 1,3,1,1
B. 1,1,1,3
C. 1,3,1,3
D. 2,3,2,3
H3PO3 + HCI When it is correctly balanced,
12. What is the correct name for Pb(CIO2h:
A. lead(II) chlorite
B. lead dichlorite
C. lead (II) chlorate
D. lead chlorate
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13. What is the correct formula for mercury(I) sulfide?
a) HgS
b) Hg2S
c) Hg2SO4
d) Hg2SO3
14. What would happen to the average kinetic energy of the molecules of a gas sample if
the temperature of the sample increased from 20°C to 40°C?
A. It would double.
B. It would become half its value.
C. It would decrease.
D. It would increase.
15. Which conditions of P and Tare most ideal for a gas?
A. low P, high T
B. high P, low T
C. high P, high T
D. depends on the gas
16. How many actual double bonds does the benzene ring possess?
A. None, carbon-carbon bonds in benzene are delocalized around the ring
B. 1 double bond
C. 2 double bonds
D. 3 double bonds
17. The functional group given below is characteristic of organic __ .
0
c-c-1c1
A. ketones
B. acids
C. aldehydes
D. esters
18. Give the IUPAC name of this compound: CH3OCH2CH3.
A. dimethyl ether
B. methoxyetha ne
C. methylethyloxide
D. propyl ether
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19. Which is NOT a physical property of alcohols or phenols?
A. Phenols are generally only slightly soluble in water.
B. The solubilities of normal primary alcohols in water decrease with increasing
molecular weight.
C. The hydroxyl group of an alcohol is non polar.
D. Due to hydrogen bonding, boiling points of alcohols are much higher than those of
corresponding alkanes.
20. The general formula for noncyclic alkynes is:
A. CnH2n
B. CnHn
C. CnH2n+2
D. CnH2n-2
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SECTIONB:
(40]
There are FOUR questions in this section. Answer all Questions.
Show clearly, where necessary, how you arrive at the answer as the working will carry marks.
Question 1
(10]
Ethylene dibromide was used as a grain pesticide until it was banned. Calculate the:
a. empirical formula and
b. molecular formula for ethylene dibromide given its approximate molar mass of 190 g/mol
and its percent composition: 12.7% C, 2.1% H, and 85.1% Br.
Question2
[8]
Given the following equation:
2.1 If 10.0 g of Al2{503)3 is reacted with 10.0 g of NaOH, determine the limiting reagent
2.2 Determine the number of moles of Al(OH) 3 produced.
2.2 Determine the number of grams of Na2S03produced.
2.4 Determine the number of grams of excess reagent left over in the reaction.
Question3
(13]
3.1 The osmotic pressure of a 0.010 M aqueous solution of CaCl2is found to be 0.674 atm at
25 °C.
a. Calculate the van't Hoff factor, i, for the solution.
(3)
b.How would you expect the value of i to change as the solution becomes more
concentrated? Explain.
(2)
3.2 At 63.5 °C the vapor pressure of H20 is 175 torr, and that of ethanol (C2HsOH)is 400 torr.
A solution is made by mixing equal masses of H20 and C2HsOH.
a. What is the mole fraction of ethanol in the solution?
{3)
b. Assuming ideal-solution behavior, what is the vapor pressure of the solution at 63.5 °C? (3)
c. What is the mole fraction of ethanol in the vapor above the solution?
(2)
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Question4
[9]
5.1 Draw all possible open-chain structures for the following molecular formulas and name
them:
(9)
a) CsH12
b) CsH,o
c) (3HsO
ENDOFEXAMINATION
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USEFULCONSTANTS:
Gas constant, R = 8.3145 J · mo1-1. K-1 = 0.083145 dm 3 · bar· mo1-1. K-1 = 0.08206 L atm mo1-1. K-
1 Pa· m 3 = 1 kPa.L = 1 N · m = 1 J
1 atm = 101 325 Pa = 760 mm Hg= 760 torr
Avogadro's Number, NA= 6.022 x 1023 mo1-1
Planck's constant, h = 6.626 x 10-34 Js
Speed of light, c = 2.998 x 108 ms-1
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PERIODIC TABLE OF THE ELEMENTS
18
I
2
H
1.00794 2
13
14
15
He
16
17 4.00260
34
5
6
7
8 9 10
Li Be
B C N 0 F Ne
6,941 9.01218
10.81 12.01 I 14.0067 15.9994 18.9984 20.179
11 12
13 14 15 16 17 18
Na Mg
Al Si p s Cl Ar
22.9898 24.305 3
4
5
6
7
8
9
10
II
12 26.9815 28.0855 30.9738 32.06 35.453 39.948
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
39.0983 40.08 44.9559 47.88 50.9415 51.996 54.9380 55.847 58.9332 58.69 63.546 6538 69.72 72.59 74.9216 78.96 79.904 83.8
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
Rb Sr y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
85.4678 87.62 88.9059 91.22 92.9064 95.94 (98) 101.07 102.906 106.42 107.868 112.41 114.82 118.69 121.75 127.6 126.9 13129
55 56 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86
Cs Ba Lu Hf Ta w Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
132.905 137.33 174.967 178.49 180.948 183.85 186207 190.2 192.22 195.08 196.967 200.59 204383 207.2 208.908 (209) (210) (222)
87 88 103 104 105 106 107 108 109 110 111 I 12
I 14
116
118
Fr Ra Lr Rf Db Sg Bh Hs Mt Uun Uuu Uub
Uuq
(223) 226.025 (260) (261) (262) (263) (264) (265) 268) (269) (272) (269)
Uuh
Uuo
Lanthanides: 57 58 59 60 61 62 63 64 65 66 67 68 69 70
La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb
138.906 140.12 140.908 14424 (145) 15036 151.96 157.25 158.925 162.50 161.930 167.26 166.934 173.04
-0
QJ
O'Q
Ill
I.C
Actinides:
89 90 91 92 93 94 95 96 97 98 99 100 IOI 102
Ac Th Pa u Np Pu Am Cm Bk Cf Es Fm Md No
.0...,
227.028 232.038 231.036 238.029 237.048 (244) (243) (247) (247) (251) (252) (257) (258) (259)
I.C
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