Chemistry past questions

  1. Organic Chemistry is the branch of Chemistry that deals with ——- and ——-
    (A) Hydrogen & oxygen
    (B) Carbon & Carbon
    (C) Carbon & Sulphur
    (D) (ANS) Carbon & Hydrogen
  2. The movement of liquid molecules from the surface of the liquid to the gaseous phase above it is known as
    (A) (ANS) Brownian motion
    (B) Zig Zag Motion
    (C) evaporation
    (D) liquefaction
  3. Which of the following is an acidic salt?
    (A) (ANS) NaHSO4
    (B) Na2SO4
    (C) CH3CO2Na
    (D) Na2S
  4. Given that the molecular mass of iron is 56 and that of oxygen is 16, how many moles of iron (III) oxide will be contained in 1kg of the compound?
    (A) 12.5moles
    (B) 0.625moles
    (C) 25moles
    (D ANS) 6.25moles
  5. 3.0g of a mixture of potassium carbonate and potassium chloride were dissolved in a 250cm3 standard flask.25cm3 of this solution required 40.00cm3 of 0.01M HCl for neutralization. What is the percentage by weight of k2CO3 in the mixture? (k = 39, O = 16, C = 12)
    (A) (ANS) 92
    (B) 89
    (C) 72
    (D) 82
  6. 0.499g of CuSO4.XH2O when heated to constant weight gave a residue of 0.346g. What is the value of X?
    (A) 2.0
    (B) 3.0
    (C) 5.0
    (D) (ANS) 4.0
  7. The principal constituents of natural gas is
    (A) (ANS) methane
    (B) ethane
    (C) propane
    (D) butane
  8. Which of the following gases can be collected by the method of downward delivery?
    (A) (ANS) chlorine
    (B) oxygen
    (C) ammonia
    (D) hydrogen
  9. A mixture of sugar and sulphur can be separated by
    (A) dissolution in water, evaporation and filtration
    (B) filtration, evaporation and dissolution in water
    (C) (ANS) dissolution in water, filtration and evaporation
    (D) evaporation, dissolution in water and filtration
  10. The percentage of water of crystallization in ZnSO4. 7H2O is
    (A) 33%
    (B) (ANS) 44%
    (C) 55%
    (D) 87%
  11. When a solution of silver (I) nitrate is saturated with hydrogen sulphide, a black precipitate forms which is
    (A) H2S
    (B) (ANS) Ag2S
    (C) PbS
    (D) HNO3
  12. 0.0075 mole of calcium trioxocarbonate (iv) is added to 0.015 mole of a solution of HCl. The volume of gas evolved at S.T.P is
    (A) 224cm3
    (B) (ANS) 168cm3
    (C) 112cm3
    (D) 100cm3
  13. The weakest attractive force that can be observed between two molecules is
    (A) ionic
    (B) covalent
    (C) coordinates
    (D) (ANS) van der waals forces
  14. Which quantum number divides shells into orbitals?
    (A) Principal
    (B) (ANS) azimuthally
    (C) magnetic
    (D) spin
  15. The major source of oxides of nitrogen is from the burning of
    (A) (ANS) coal
    (B) wood
    (C) fuel
    (D) chlorofluorocarbons.
  16. Cotton is almost pure
    (A) starch
    (B) protein
    (C) animal fibre
    (D) (ANS) cellulose
  17. Lucas reagent is used to test for
    (A) alkanes
    (B) alkanoic acids
    (C) (ANS) alkanols
    (D) amines
  18. An element X forms the following compounds with chlorine: XCl4, XCl3, XCl2. This illustrate the
    (A) law of multiple proportions
    (B) (ANS) law of definite proportions
    (C) law of conservation of mass
    (D) law of chemical proportions
  19. The molecular formula of a common organic laboratory anesthetic is
    (A) (ANS) CHCl3
    (B) CHI3
    (C) CCl4
    (D) CHF3
  20. Organic molecules that have the suffix-ene are unsaturated hydrocarbons that have
    (A) a single bond
    (B) (ANS) double bond
    (C) a triple bond
    (D) an ionic bond
  21. Copper metal dissolves in concentrated trioxonitrate (v) acid with the resultant evolution of
    (A) CO2
    (B) SO2
    (C) (ANS) NO2
    (D) CO
  22. Which of the following is not a member of the homologous series of the paraffins?
    (A) C3H8
    (B) C5H12
    (C) C15H32
    (D) (ANS) C24H48
  23. Element P, Q, R and S have 6, 11, 15 and 16 electrons respectively, therefore,
    (A) p will form an ionic bond with R
    (B) R will form an electrovalent bond with S
    (C) Q will form a covalent bond with S
    (D) (ANS) Q will form an electrovalent bond with S
  24. A gaseous mixture of 80.0g of oxygen and 56.0g of nitrogen has a total pressure of 1.8atm. The partial pressure of oxygen in the mixture is
    (A) 0.8atm
    (B) (ANS) 1.0atm
    (C) 1.2atm
    (D) 1.4atm
  25. Palm wine turns sour with time because
    (A) the sugar content is converted into alcohol
    (B) the CO2 formed during the fermentation process has a sour taste
    (C) it is commonly adulterated by the tappers and sellers
    (D) (ANS) microbiological activity results in the production of organic acids within it.
  26. Alkanals can be differentiated from alkanones by reaction with
    (A) 2, 4 – dinitrophenylhydrazine
    (B) hydrogen cyanide
    (C) sodium hydrogen sulphite
    (D) (ANS) Tollen’s reagent
  27. The following are uses of sulphur except
    (A) vulcanization of rubber
    (B) manufacture of dyes
    (C) coating of steel to prevent rusting
    (D) (ANS) manufacture of tetraoxosulphate (VI) acid.
  28. Catalytic hydrogenation of benzene produces
    (A) an aromatic hydrogenation
    (B) margarine
    (C) (ANS) cyclohexane
    (D) benzene
  29. The oxidation number of chlorine is +1in
    (A) KClO3
    (B) Cl2O7
    (C) ZnCl2
    (D) (ANS) NaClO
  30. The carbon atoms on ethane are
    (A) Sp2 hybridised
    (B) SP hybridized
    (C) (ANS) SP3 hybridised
    (D) SP2d hybridized
  31. At 25oC and 1atm, a gas occupies a volume of 1.50dm3. What volume will it occupy at 100 oC and 1atm?
    (A) (ANS) 1.88dm3
    (B) 6.00dm3
    (C) 18.80dm3
    (D) 60.0dm3
  32. A current of 4.0 amperes was passed through copper (II) tetraoxosulphate (IV) solution for one hour using copper electrodes. What was the mass of copper deposited? (Cu =64, IF = 96500C)
    (A) 3.2g
    (B) 4.8g
    (C) 6.4g
    (D) (ANS) 96
  33. Pauli exclusion principle is related to
    (A) quantum numbers of electrons
    (B) (ANS) reversibility of equilibrium reactions
    (C) electronegativity values of elements
    (D) collision theory of reactions rate
  34. Esterification of propane 1, 2, 3-triol and unsaturated higher carboxylic acids will produce
    (A) fats
    (B) soap
    (C) alkanols
    (D) (ANS) methyl propanoate
  35. The greenhouse effect is a climatic condition associated with the presence of excess
    (A) (ANS) CO2
    (B) H2S
    (C) NO
    (D) NH3
  36. The metal extracted from cassiterite is
    (A) calcium
    (B) copper
    (C) tin
    (D) (ANS) sodium
  37. The following are uses of sulphur except
    (A) vulcanization of rubber
    (B) manufacture of dyes
    (C) (ANS) coating of steel to prevent rusting
    (D) manufacture of tetraoxosulphate (VI) acid
  38. Equilibrium is sad to be attained in a reversible reaction when
    (A) all the reactants have been used up
    (B) all the products have been formed
    (C) (ANS) there is no further change in temperature
    (D) the rate of forward and backward reactions are equal
  39. The greenhouse effect is a climatic condition associated with the presence of excess
    (A) (ANS) CO2
    (B) H2S
    (C) NO
    (D) NH3
  40. The following uses radioactive isotopes except for
    (A) sterilization of medical equipment
    (B) tracing reaction paths
    (C) dating elements
    (D) (ANS) determining equilibrium positions
  41. Which of the following is needed to produce a slag during the extraction of iron in the blast furnace?
    (A) cryolite
    (B) (ANS) limestone
    (C) carbon
    (D) sulphur
  42. Calcium atom ionizes by
    (A) gaining two electrons
    (B) (ANS) losing two electrons
    (C) sharing two electrons
    (D) gaining two proton
  43. In the Periodic Table, the elements that lose electrons most readily belong to
    (A) (ANS) group IA
    (B) group IIA
    (C) group IIIA
    (D) group VIIA
  44. Which of the following halogens is the most reactive?
    (A) (ANS) F2
    (B) Br2
    (C) Cl2
    (D) I2
  45. Which of the following substances increases in mass when heated in air?
    (A) sodium chloride
    (B) iodine crystals
    (C) (ANS) magnessium ribon
    (D) copper (ii) oxide
  46. Which of the following properties increases down a group in the Periodic Table
    (A) (ANS) atomic radius
    (B) electronegativity
    (C) electron affinity
    (D) ionization energy
  47. Which of the following types of reactions takes place between C2H4 and the halogens?
    (A) Substitution
    (B) (ANS) Addition
    (C) polymerization
    (D) Oxidation
  48. An amphoteric oxide is an
    (A) amorphorous oxide of a metal
    (B) amorphorous oxide of a non-metal
    (C) Oxide that is insoluble in water
    (D) (ANS) Oxide that behaves as a base as well as an acid
  49. What weight of sodium hydroxide is required to make 500cm3 of 0.2M solution?
    (A) 40g
    (B) 20g
    (C) (ANS) 10g
    (D) 4g
  50. The IUPAC names for the compounds CH3COOH and CH2 = CH2 are respectively;
    (A) (ANS) acetic acid and ethane
    (B) ethanoic acid and ethene
    (C) methanoic acid and ethylene
    (D) acetic acid and ethene

PRACTICE 2

Question 1
A secondary alkanol can be oxidized to give an
Options
A)
alkanone
B)
alkyne
C)
alkanoic acid
D)
alkanal
The correct answer is A.
Explanation:
When an secondary alcohol is treated with acidified KMnO4, or K2Cr2O7, they yield an alkanone
Explanation provided by Jor Jagaba
Explanation provided by Jonathan Hussaini
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Question 2
Which of the following will give a precipitate with an aqueous solution of copper (I) chloride?
Options
A) But-2-ene
B) But-1-ene
C) But-2-yne
D) But-1-yne
The correct answer is D.
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Question 3
The IUPAC name for CH33CH22COOCH22CH33 is
Options
A) methylpropanoate
B) ethylethanoate
C) ethylpropanoate
D) methylethanoate
The correct answer is C.
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Question 4
A certain hydrocarbon on complete combustion at s.t.p produced 89.6dm33 of CO22 and 54g of water. The hydrocarbon should be
Options
A) C66H66
B) C44H1010
C) C55H1010
D) C44H66
The correct answer is D.
Explanation:
In the question above an Hydrocarbon combust to give CO2 and H20
Let Hydrocarbon be
CxHy + x+Y/4O2= xCO2 + Y/2H2O
Mass of C0=44g and H2O=18g
at STP vol= 22.4
Therefore, 1mole of CO2 contains 44g and 22.4dm³ at STP
1mole = 22.4dm³
xmole = 89.6dm³
Cross multiplying x=89.6/22.4 =4mole of CO2 produce
1mole of H2O = 18g
Xmole = 56g
Cross multiplying
X = 56/18 = 3mole of H20
Then….
CxHy + X + y/4O2 = 4CO2+ 3H2O
Balancing
C4H6 + 6O2 = 4CO2 + 3H2O
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Question 5
2-methylprop-1-ene is an isomer of
Options
A) 3-methyl but-1-ene
B) 2-methyl but-1-ene
C) but-2-ene
D) pent-2-ene
The correct answer is C.
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Question 6
Hydrocarbons which will react with Tollen’s reagent conform to the general formula
Options
A) CnnH2n2n
B) CnnH2n+22n+2
C) CnnH2n−22n−2
D) CnnH2n+12n+1OH
The correct answer is C.
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Question 7
The IUPAC name of the compound CF33CHBrCl is
Options
A) 2-chloro-2-bromo-1,1,1-trifluoroethane
B) 2-bromo-2-chloro-1,1,1-trifluoroethane
C) 1-bromo-1-chloro-2,2,2-trifluoroethane
D) 1,1,1-trifluoro-2-bromo-2-chloroethane
The correct answer is B.
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Question 8
A synthetic rubber is obtained from the polymerization of
Options
A) neoprene
B) isoprene
C) butandiene
D) propylene
The correct answer is B.
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Question 9
Burning magnesium ribbon in air removes which of the following
(i) oxygen (ii) nitrogen (iii) argon and (iv) carbon(iv)oxide?
Options
A) i and iv only
B) i, ii, iii and iv only
C) i only
D) i and ii only
The correct answer is C.
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Question 10
Which of the following is the best starting material for the preparation of oxygen? Heating of trioxonitrate (v) with
Options
A) Pb
B) Zn
C) Ca
D) Na
The correct answer is A.
Question 11
Which of the following metals is the most essential in the regulation of blood volume, blood pressure and osmotic equilibrium?
Options
A) Zinc
B) Manganese
C) Sodium
D) Iron
The correct answer is C.
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Question 12
Which of the following alkaline metals react more quickly spontaneously with water?
Options
A) Calcium
B) Beryllium
C) Magnesium
D) Strontium
The correct answer is A.
Explanation:
The alkaline earth metals (Be, Mg, Ca, Sr, Ba, and Ra) are the second most reactive metals in the periodic table, and, like the Group 1 metals, have increasing reactivity in the higher periods. Beryllium (Be) is the only alkaline earth metal that does not react with water or steam, even if metal is heated to red heat. Additionally, beryllium has a resistant outer oxide layer that lowers its reactivity at lower temperatures.
Magnesium shows insignificant reaction with water, but burns vigorously with steam or water vapor to produce white magnesium oxide and hydrogen gas:
Mg(s) + 2 H2O(l) ⟶ Mg(OH)2(s) + H2(g)
A metal reacting with cold water will produce metal hydroxide. However, if a metal reacts with steam, like magnesium, metal oxide is produced as a result of metal hydroxides splitting upon heating.
The hydroxides of calcium, strontium and barium are only slightly water-soluble but produce sufficient hydroxide ions to make the environment basic, giving a general equation of:
M(s) + 2 H2O(l) ⟶ M(OH)2(aq) + H2(g)
Order of reactivity Metal Reactions with water or steam
most reactive potassium (K) very vigorous reaction with cold water
↑ sodium (Na) vigorous reaction with cold water
↓ calcium (Ca) less vigorous reaction with cold water
least reactive magnesium (Mg) slow reaction with cold water, vigorous with steam
• If metals react with cold water, hydroxides are produced.
• Metals that react with steam form oxides.
• Hydrogen is always produced when a metal reacts with cold water or steam.
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Question 13
When chlorine water is exposed to bright sunlight, the following products are formed
Options
A) HCl(aq)(aq) and Cl22
B) HOCl(aq)(aq) and Cl22
C) HCl(aq)(aq) and O22
D) HOCl(aq)(aq) and O22
The correct answer is C.
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Question 14
Which process(es) is/are involved in the turning of starch iodide paper blue-black by chlorine gas?
Options
A) chlorine attacks the starch to give the blue-black color
B) chlorine attacks the iodide ion to give the blue-black color
C) chlorine oxidizes the iodide ion to produce iodine which attacks the starch to give the blue-black color
D) iodine attacks the starch to give the blue-black color
The correct answer is C.
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Question 15
Which of the following is a set of neutral oxides?
Options
A) N22O, H22O, CO
B) N22O, SO22, CO
C) N22O, Na22O, ZnO
D) N22O, SO33, NO
The correct answer is A.
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Question 16
SO33 is not directly dissolved in water in the industrial preparation of H22SO44 by the contact process because
Options
A) SO33 is an acidic gas
B) Acid is usually added to water and not water to acid
C) The reaction between SO33 and water is violently exothermic
D) SO33 does not dissolve readily in water
The correct answer is C.
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Question 17
Which of the following statements does not show Rutherford’s account of Nuclear Theory? An atom contains a region
Options
A) which contains protons and neutrons
B) which is positively charged
C) which is massive and can cause deflection of a few projectiles
D) which is very large and in which close to 98% of projectiles pass undeflected
The correct answer is C.
Explanation:
Rutherford’s account of Nuclear theory does not include the fact that atoms contain a massive region and cause deflection of from projectiles.
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Question 18
Elements X and Y have electronic configurations 1s222s222p44 and 1s222s222p663s223p11 respectively. When they combine, the formula of the compound formed is
Options
A) XY
B) X22Y
C) Y22X33
D) X22Y33
The correct answer is C.
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Question 19
By what amount must the temperature of 200cm33 of Nitrogen at 27°C be increased to double the pressure if the final volume is 150cm33 (Assume ideality)
Options
A) 150°C
B) 177°C
C) 75°C
D) 120°C
The correct answer is B.
Explanation:
Using the ideal gas law and equation:
P1V1T1=P2V2T2P1V1T1=P2V2T2
P1×200cm3300K=2P×150cm3T2P1×200cm3300K=2P×150cm3T2
Cross multiply:
T2=300×150×2P200×PT2=300×150×2P200×P
=450K=450K or 177∘C177∘C
Don’t forget to convert to ∘C∘C
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Question 20
The combustion of carbon(ii)oxide in oxygen can be represented by equation.
2CO + O22 → 2CO22
Calculate the volume of the resulting mixture at the end of the reaction if 50cm33 of carbon(ii)oxide was exploded in 100cm33 of oxygen
Options
A) 75cm33
B) 125cm33
C) 100cm33
D) 50cm33
The correct answer is B.
Question 21
When ammonia and hydrogen ion bond together to form ammonium ion, the bond formed is called
Options
A) electrovalent bond
B) co-ordinate bond
C) ionic bond
D) covalent bond
The correct answer is B.
Explanation:
When ammonia and hydrogen ion go into bonding, they form ammonium ion by combining with a dative/coordinate covalent bond.
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Question 22
Which of the following represents the kind of bonding present in ammonium chloride?
Options
A) ionic only
B) covalent only
C) ionic and dative covalent
D) dative covalent
The correct answer is C.
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Question 23
Consider the reaction
A(s)(s) + 2B(g)(g) → 2C(aq)(aq) + D(g)(g)
What will be the effect of a decrease in pressure on the reaction?
Options
A) the equilibrium will shift
B) rate of forward reaction will increase
C) rate of backward reaction will increase
D) rates of forward and backward reaction are not affected
The correct answer is B.
Explanation:
Given: The equation below
A(s)(s) + 2B(g)(g) → 2C(aq)(aq) + D(g)(g)
Since we have a higher number of moles of gaseous species on the LHS, i.e 2, a decrease in pressure will favor the forward reaction.
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Question 24
For the general equation of the nature
XP + yQ ⇌ mR + nS, the expression for the equilibrium constant is
Options
A) k[Pxx[Qyy
B) m[R[Sx[Py[Qm[R[Sx[Py[Q
C) [Px[Qy[Rm[Sn[Px[Qy[Rm[Sn
D) [Rm[Sn[Px[Qy[Rm[Sn[Px[Qy
The correct answer is D.
Explanation:
Given:
xP + yQ ⇌ mR + nS
Let us assume they are all in aqueous solution
k = [Rm[Sn[Px[Qy[Rm[Sn[Px[Qy
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Question 25
Which of the following reactions is an oxidation process?
Options
A) 2H++ + 2e−− →→ H22
B) 2O2−2− + 4e−− →→ O22
C) OCl−− + H22O + 2e−− →→ 2OH−− + Cl−−
D) Cl + e−− →→ Cl−−
The correct answer is B.
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Question 26
If acidified Potassium Dichromate(VI) (K22Cr22O77) acts as oxidizing agent, color changes from
Options
A) yellow to green
B) orange to green
C) yellow to red
D) orange to red
The correct answer is B.
Explanation:
Potassium dichromate is an oxidising agent in organic chemistry. It is used to oxidize alcohols.
In an aqueous solution the color change exhibited can be used to test for distinguishing aldehydes from ketones. Aldehydes reduce dichromate from the +6 to the +3 oxidation state, changing color from orange to green. This color change arises because the aldehyde can be oxidized to the corresponding carboxylic acid.
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Question 27
The heat of formation of ethene, C22H44 is 50 kJmol−1−1, and that of ethane, C22H66 is -82kJmol−1−1. Calculate the heat evolved in the process:
C22H44 + H22 →→ C22H66
Options
A) -122kJ
B) -132kJ
C) -88kJ
D) -60kJ
The correct answer is B.
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Question 28
Which of the following statements about catalyst is false?
Options
A) biological catalysts are called enzymes
B) catalyst do not appear in the balanced equation
C) catalyst reduce the activation energy for a reaction
D) catalysts do not alter the mechanism of the reaction and never appear in the rate low
The correct answer is D.
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Question 29
Which of the following does not support the fact that air is a mixture?
Options
A) the constituents of air are in a fixed proportion by mass
B) it cannot be represented with a chemical formula
C) the constituents of air can be separated by physical by physical means
D) none of the above
The correct answer is A.
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Question 30
What technique is suitable for separating a binary solution of potassium chloride and potassium trioxochlorate (V)?
Options
A) Fractional crystallization
B) Fractional distillation
C) Filtration
D) Evaporation
The correct answer is A.
Question 31
At 27°C, 58.5g of sodium chloride is present in 250cm33 of a solution. The solubility of sodium chloride at this temperature is?
(molar mass of sodium chloride = 111.0gmol−1−1)
Options
A) 2.0 moldm−3−3
B) 0.25 moldm−3−3
C) 1.0 moldm−3−3
D) 0.5 moldm−3−3
The correct answer is A.
Explanation:
Given the Mass of the salt = 58.5g
Volume = 250 cm33 = 0.25 dm33
Mass concentration = MassVolumeMassVolume
= 58.50.2558.50.25 = 234 gdm−3−3
Solubility (in moldm−3−3 = 234111234111
= 2.11 moldm−3−3
≊≊ 2.0 moldm−3−3
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Question 32
Which of the following properties increases from left to right along the period but decreases down the group in the Periodic Table?
I. Atomic Number ii. Ionization energy iii. Metallic character iv. Electron affinity
Options
A) ii and iii only
B) ii and iv only
C) iii and iv only
D) i and ii only
The correct answer is B.
Explanation:
Ionization energy and electron affinity increase across a period, and decrease down a group.
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Question 33
The molecular shape and bond angle of water are respectively
Options
A) linear, 180°
B) bent, 109.5°
C) tetrahedral, 109.5°
D) bent, 105°
The correct answer is D.
Explanation:

The shape of water molecule = Bent/ V- shaped
The bond angle of water = 104.5°/ 105°
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Question 34
Na22CO33 + 2HCl →→ 2NaCl + H22O + CO22
The indicator most suitable for this reaction should have a pH equal to
Options
A) 5
B) 7
C) 3
D) 9
The correct answer is C.
Explanation:
Methyl orange is the best indicator for the reaction with range 3.1 – 4.4.
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Question 35
A radioactive nucleus has a half-life of 20 years, starting with 100,000 particles, how many particles will be left exactly at the end of 40 years
Options
A) 75,000 particles
B) 35,000 particles
C) 25,000 particles
D) 50,000 particles
The correct answer is C.
Explanation:
Given:
t(_{\frac{1}{2}) = 20 years
After the first 20 years, half of the substance (12×100,000=50,00012×100,000=50,000) will have decayed. Hence, we have 100,000 – 50,000 = 50,000 particles left.
After the second 20 years (being 40 years in all), half of the remaining substance (12×50,000=25,00012×50,000=25,000) will have decayed.
Remaining particles after 40 years = 50,000 – 25,000
= 25,000 particles.
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Question 36
Which two gases can be used for the demonstration of the fountain experiment?
Options
A) SO33 and NH33
B) SO22 and NH33
C) HCl and NH33
D) SO22 and HCl
The correct answer is C.
Explanation:
Two gases that can be used in the study of fountain experiment is ammonia gas and hydrogen chloride gas. The experiment introduces concepts like solubility and the gas laws at the entry level.
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Question 37
Which of the following pollutants will lead to the depletion of ozone layer?
Options
A) chlorofluorocarbon
B) carbon (ii) oxide
C) hydrogen sulphide
D) sulphur (iv) oxide
The correct answer is A.
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Question 38
Which of the following describes the chemical property of acids?
Options
A) None of the above
B) Acid + XCO33 →→ Salt + H22O + NH33
C) Acid + NaOH →→ Normal salt + CO22
D) Acid + XnnCO33 →→ Salt + H22O + CO22
The correct answer is D.
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Question 39
Which of the following pairs cannot be represented with a chemical formula?
Options
A) air and bronze
B) bronze and sodium chloride
C) copper and sodium chloride
D) caustic soda and washing soda
The correct answer is A.
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Question 40
Consider the equation below:
Cr22O2−772− + 6Fe2+2+ + 14H++ →→ 2Cr3+3+ + 6Fe3+3+ + 7H22O.
The oxidation number of chromium changes from
Options
A) +5 to +3
B) +6 to +3
C) -2 to +3
D) +7 to +3
The correct answer is B.
Explanation:
Cr22O2−772− + 6Fe2+2+ + 14H++ →→ 2Cr3+3+ + 6Fe3+3+ + 7H22O
The oxidation of Cr in Cr22O2−772− :
Let the oxidation of Cr = x;
2x + (-2 x 7) = -2 ⟹⟹ 2x – 14 = -2
2x = 12 ; x = +6
Hence, the change in oxidation of Cr = +6 to +3
Question 41
Which of the following is a physical change?
Options
A) Exposing white phosphorus to air
B) Burning kerosene
C) Dissolving calcium in water
D) Freezing ice cream
The correct answer is D.
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Question 42
In the reaction between sodium hydroxide and tetraoxosulphate (VI) solutions, what volume of 0.5 molar sodium hydroxide would exactly neutralize 10cm33 of 1.25 molar tetraoxosulphate (vi) acid?
Options
A) 25cm33
B) 10cm33
C) 20cm33
D) 50cm33
The correct answer is D.
Explanation:
Equation of reaction : 2NaOH + H22SO44 → Na22SO44 + 2H22O
Concentration of a base, CB = 0.5M
Volume of acid, VAA = 10cm33
Concentration of an acid, CAA = 1.25M
Volume of base, VBB = ?
Recall:
CAVACBVB=nAnBCAVACBVB=nAnB … (1)
N.B: From the equation,
nAnB=12nAnB=12
From (1)
1.25×100.5×VB=121.25×100.5×VB=12
12.50.5VB=1212.50.5VB=12
25 = 0.5VBB
VB = 50.0 cm33
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Question 43
Sulphur exists in six forms in the solid state. This property is known as
Options
A) Isomerism
B) Allotropy
C) Isotopy
D) Isomorphism
The correct answer is B.
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Question 44
In the reaction:
M + N → P
ΔH = +Q kJWhich of the following would increase the concentration of the product?
Options
A) Adding a suitable catalyst
B) Increasing the concentration of P
C) Increasing the temperature
D) Decreasing the temperature
The correct answer is C.
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Question 45
A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen. If the molar mass of the compound is 180. Find the molecular formula.
[H = 1, C = 12, O = 16
Options
A) C33H66O33
B) C66H66O33
C) C66H1212O66
D) CH22O
The correct answer is C.
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Question 46
The IUPAC nomenclature of the compound
H33C – CH(CH33) – CH(CH33) – CH22 – CH33
Options
A) 3,4- dimethylhexane
B) 2,3- dimethyl pentane
C) 2- ethyl hexane
D) 2,3- dimethylhexane
The correct answer is B.
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Question 47
Which of the following gases contains the least number of atoms at s.t.p?
Options
A) 1 mole of butane
B) 4 moles of chlorine
C) 3 moles of ozone
D) 7 moles of argon
The correct answer is A.
Explanation:
4 moles of chlorine gas = 4Cl22 = 8 atoms of chlorine
3 moles of ozone = 3O33 = 9 atoms of oxygen
1 mole of butane = C44H1010
7 mole of argon = 7Ar = 7 atoms of argon
Butane has the least number of atoms.
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Question 48
What mass of magnesium would be obtained by passing a current of 2 amperes for 2 hours, through molten magnesium chloride?
[1 faraday = 96500C, Mg = 24
Options
A) 1.12g
B) 4.48g
C) 1.80g
D) 2.00g
The correct answer is C.
Explanation:
Given:
Current (I) = 2A; Time (t) = 2 hours = 7200 secs
Q = It
= 2 x 7200 = 14400C
1 F = 96500C
x = 14400C
x = 14400965001440096500
= 0.15F
Mg2+2+ + 2e−− →→ Mg
2F →→ 24g
0.15F →→ x
2x = 24 x 0.15
x = 24×0.15224×0.152
= 1.8g
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Question 49
Which important nitrogen-containing compound is produced in Haber’s process?
Options
A) NH33
B) NO22
C) NO
D) HNO33
The correct answer is A.
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Question 50
Elements in the periodic table are arranged in the order of their
Options
A) atomic numbers
B) metallic character
C) mass number
D) relative atomic mass
The correct answer is A.

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