OAU CHEMISTRY 2010 POST-UTME PLUS ANSWERS

OAU CHEMISTRY 2010 POST-UTME  

1. Whose experiment showed that the atom has a tiny positively charged nucleus?
a) Thompson b) Rutherford
c) Millikan d) Dalton
2. Which of the quantum number divides shells into orbitals?
a) Principal b) subsidiary
c) magnetic d) spin
3. Which of these statements is/are correct of a proton?
i. The mass of a proton is one-twelfth the molar mass of carbon
ii. The mass of a proton is 1840 times the mass of an electron
iii. The mass of a proton is 1 .0008g
a) ii only  b) i,ii and iii
c) i only   d) i and ii only
4. The following are chemical entities identifiable during qualitative analysis
i) SO2-4  ii) H3O+ iii) NH+ iv) OH.Which of them can be detected by litmus paper?
a)ii and iv only b) ii only
c) i & iii only d) I & ii only
5. i) NaHCO3 ii) NaHSO4 iii) NaCI. Which of these will dissolve in water to N give alkaline N solution?
a) i, ii and iii b) ii only
c) i only d) i & ii only
6. Burning of 0.46g of ethanol produced heat that raised the temperature of 100g of water
by 30°C. Calculate the heat of combustion of ethanol. C2H5OH. (C = 12, H= 1; 0=16)
a) 50kJmol-1 b) 900kJmol
c) l200kJrnol-1 d)l000kJmol-1
7. When chlorine is bubbled into potassium iodine solution
a) A white precipitate is seen (sorry will be completed later)
8. PCl5 PCI3(q) + Cl2. In reaction above,an increase in pressure will
a) Decelerate the reaction
b) increase the yield of PCI3
c) increase the yield of PCI5
d) accelerate the reaction.
9. A saturated solution of silver trioxocarbonate(IV), was found to have
concentration of 1.30 x 10-5mo1 dm3. The solubility product of trioxocarboate (IV) is
a) 8.79 x 10-10 b) 1.69 x 10-10
c) 1.82 x 10-10 d) 9.84 x 10-10
10. A zinc half-cell is connected to an iron half- cell through a salt bridge and both are also connected through a copper wire. At which electrode is reduction taking place and which electrode is positively charged?
a) Zinc, zinc b) iron, iron
c) zinc, iron d) iron, zinc
11. Which of the following is the difference between an electrolytic cell X and electrochemical cell Y
a) Anode in X is -ve while anode in Y is +ve
b) In X, oxidation takes place at the anode while in Y reduction takes place at the anode
c) In X, anode is positive while in Y anode is negative.
d) In X, chemical energy is converted into electrical energy while in Y electrical energy is converted into chemical energy.
12. What mass of bromine will saturate completely 6.8g of 3-methybut-1-yne (H = 1; C= 12; Br = 80)
a) 16g  b) 32g
c) 12g  d) 24g
13. 100cm3 of oxygen and 10cm3 of butane measured at room temperature and
pressure were mixed and exploded. Determine the volume of the mixture when brought back

to the original conditions of measurements.
a) 125cm3 b) 110cm3
c) 75cm3 d) None of these
14. Sulphur
a) Forms two alkaline oxides
b) is spontaneously inflammable
c) burns with a blue flame
d) conducts electricity in the molten state.
15. Candidate devised the following for the separation of the components of
some mixtures
i. Components of ink, principles involved is chromatography
ii. Components of water and kerosene principle involved is separating funnel
iii. Components of iodine and sodium chloride, principles involved is sublimation.
In which of the above is the principle correct?
a) i only b) ii only
c) iii only d) i, ii & iii
16. Which of the following procedures will separate a mixture of sand, sodium
chloride and iodine into its components?
a) Add water, filter, sublime, evaporate to dryness
b) Add water, sublime, filter, evaporate to dryness
c) Sublime, filter, add water, evaporate to dryness
d) Sublime; add water; filter; evaporate to dryness
17. The type of bonds in ammonium chloride are
a) Covalent and electrovalent
b) dative and covalent
c) dative and electrovalent
d) covalent, dative and electrovalent
18. Which of the following types of bonding does not produce a compound
a) ionic bonding
b) covalent bonding
c) dative bonding
d) metallic bonding
19. The combining powers of HCO3 O; Na; Cl; respectively are
a) -2 +1, -1. +1 b) 1.2.1,
c) +1. -2, +1.1 d) none of these
20. What is the chemical formula of the compound containing 6.02 x 1023 atoms of hydrogen, 35g of chlorine, and 4 moles of oxygen atoms?
a) HCI4O
c) HCl3O4 INCOMPLETE
21. 200cm3 of hydrogen were collected over water at 30 and 740mm of Hg.Calculate the
volume of the gas at s.t.p. if thc vapour pressure of water at the temperature of the experiment is 14mm of Hg.
a) 168.25cm3 b) 176.40 cm3
c) 185.46 cm3 d) 172.14 cm3
22. A given mass of gas occupies a certain volume at 300K. At what temperature will its volume be double?
a) 400K  b) 480K
c) 550K  d) 600K
23. The basic assumption in the kinetic theory of gas that “forces of attraction and repulsion between gaseous molecules are negligible” implies that:
a) Molecules will continue their motion indefinitely
b) Gases will occupy any available space
c) Gases can be compressed
d) None of the above
24. Which of the following is true of a sample of hydrogen gas whose mass is 4.00g under a pressure of 2atm and a temperature of 27°C? (H = 1, R = 0.032 lit
atm. Mol-1 deg-1)
a) Its volume is 24.6 litres  b) it contains 6.02 x 1023 molecules
c) it exists as atoms because of temperature  d) none of the above
25. Which of the following combination of reagents will react to give chlorine
gas?
a) Sodium chloride, conc. H2SO4 and Manganese(IV) oxide
b) Potassium tetraoxomagnate HCIO d) HCI2O4
c) Potassium trioxochlonde(v) and conc. H2SO4
d) Potassium tetraoxomagnate(VI) and conc. H2SO4.

ANSWER KEY

1B 6C 11C 16D 21D
2B 7B 12B 17D 22D
3B 8C 13A 18D 23D
4C 9A 14C 19B 24A
5C bC 15D 20C 25A

Explanations to the Questions.

1. Rutherford suggested an atomic model (the nuclear model) in which an atom
has a small-positively charged centre (nucleus). where nearly all the mass is
concentrated,surrounding the nucleus is a large space (extra-nuclear point) containing the
electrons (B)
2. The subsiding or azimuthal quantum number, I has integral values ranging
from 0 to (n— 1). The electrons with subsidiary quantum numbers 0. 1, 2, and 3 are usually
referred to as the s, p, d and f — electrons respectively. Thus, this quantum number
shows how many energy level that are in each electron shell (B)
3. (B) — check relevant chemistry for clarification.
4. NH+4 will release NH3 gas (basic) while
SO2-4 will release SO2 gas (acidic) (C)
5. NaHCO3 + H2O → H2CO3 + NaOH
NaHSO4 + H2O→Na+ + SO42- + H3O+NaCl is neutral (C)
6. ΔHI = mcθ = 100g x 4. Jg 1k-1 x 303K21= 127,260J127.26 0J
No of mole = 0.01mole 0.0-1 ,na = 12,726,000Jmol-1 = 12,726kJmol-1 (exothermic)
7. Cl2 + 2Kl → 2KCI + 12 The colouration is due to the formation of iodine (B)
8. PCIs(g) — PCI3(g) + Cl2(g).Since the products are in gaseous form, increase in pressure will lead to decrease in volume, this force the products to move closer and combine to form parent compound,thereby cause increase in the yield of PCI5 (C) = (2.6 x 05mol/dm3) 2(1.30x l0-5 mol/dm3) = 8.788 x 10-5mol3dm9 (A)
10. Iron (Fe) is below zinc in the electrochemical series, hence iron is a less electropositive element compared to zinc. This makes zinc to be a stronger reducing agent since reduction takes place at the cathode, zinc is used as cathode while iron will be anode (C)
11. In electrolyte cell, the cathode is the negative electrode while anode is
the positive electrode. In electrochemical cell, the cathode is positive electrode while
the anode is negative (C)
12. CH3CH(CH3)=CH+Br2→ CH3CH(CH3)C Br2,-CBr2 Imole 2mole Imole68
No. of mole = 68 = 0.10mole 3 — methylbut-I-yne I mole of 3-methylbut-I-yne requires 2 moles of Br2 0.10 mole of 3-methylbut- 1 -yne produces 2 x 0.10 of Br21 = 0.20 mole of Br2
Mass of Br2 = 0.2 x 160 =32grams (B)
13. C4H10 + 2 O2 → 4CO2 + 5H2O Reacting mole 1mole 4 mole 5 mole Available vol. 10cm 100cm3 Reacting vol. 10 cm3 65cm3 40cm3 35cm3— Residual gas = 35 + 40 + 50 = 125 cm3 (A)
14. When sulphur is heated in a partial supply of air, it burns with bright
blue flame to form sulphur(IV) oxide and small amount of SO3 S(s) + O2(g) →SO2(g)
15. (D)
16. Heat the mixture to sublime iodine which will go into gaseous form and
collected separately. The left mixture is dissolve in water while the hall dissolve in
water and it is filtered to separate sand from the mixture while the residual is heated to
dryness to recover the NaCI (D)
17. In NH4CI, there is ionic bond between NH+4 &Cl-. There are three pure covalent
bonds and one coordinate covalent (dative) bond. The bond types in NH4CI are
ionic,covalent and coordinate covalent (three types) (D)
18.D
19.Combing power of HCO-3 = 1O=2Alkaline metal, Na = 1Halogen, Cl =1 (B)
20. 6.02 x 1023 atoms of hydrogen give 1mole of hydrogen 35g of chlorine give
1mole of chlorine.4moles of oxygen atoms give 4 oxygen atoms Combination give HCIO4 (C)
21 P1 = 740 – 14= 726mmHg V1 = 20cm3 T1 = 30°C + 273= 303KP2 = S.t.p= 76OmmHgT2 = s.t.p= 273K V2 = PVT

TO BE COMPLETED LATER

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2 comments on “OAU CHEMISTRY 2010 POST-UTME PLUS ANSWERS

  1. Pingback: OAU CHEMISTRY 2009 POST-UME | LAGOSBOOKSCLUB.WORDPRESS.COM

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