General Chemistry I — 2024 Past Questions

Lagos State University CHM101: 66 questions.

Topics: Atoms, elements, molecules, Chemical bonding and intermolecular forces, Chemical equations and stoichiometry, Modern electronic theory of atoms, Periodicity and building up of the periodic table, Kinetic theory of matter, Acids, bases and salts, Valence, Redox reactions and introduction to electrochemistry, Hybridisation and shapes of simple molecules, Electronic configuration

  1. The [H₃O⁺] in 0.250 M benzoic acid (HC₇H₅O₂) is 3.9 × 10⁻³ M. Calculate Ka.
    1. 6.2 × 10⁻⁵
    2. 6.2 × 10⁵
    3. 6.1 × 10⁻⁵
    4. 6.3 × 10⁻⁵
  2. Calculate the approximate [H₃O⁺] in a 0.220 M solution of hypochlorous acid. Ka for HOCl = 3.0 × 10⁻⁸.
    1. 8.1 × 10⁻⁵ M
    2. 7.1 × 10⁻⁵ M
    3. 8.3 × 10⁻⁵ M
    4. 8.5 × 10⁻⁵ M
  3. An organic compound with molecular mass 113 has the following percentage composition: C = 53.12%, N = 12.4%, O = 28.32% and H = 6.2%. What is its molecular formula?
    1. C₃H₇NO₂
    2. C₂H₆NO₂
    3. (C₃H₃NO₇)₂
    4. C₅H₇NO₂
  4. Determine the osmotic pressure of a solution containing 2.77 g of caffeine (C₈H₁₀N₄O₂, M = 194.2 g/mol) dissolved in 20 mL of solution at 273 K.
    1. 20.7 atm
    2. 16.0 atm
    3. 22.6 atm
    4. 30.7 atm
  5. Calculate the boiling point of a solution made by dissolving 2.77 g of non-volatile caffeine (C₈H₁₀N₄O₂, M = 194.2 g/mol) in 12.8 mL of chloroform. For chloroform, Kb = 3.63 °C kg/mol, density = 1.483 g/mL and normal boiling point = 61.2 °C.
    1. 61.2 °C
    2. 63.9 °C
    3. 103.6 °C
    4. 2.7 °C
  6. The de Broglie wavelength of a tennis ball of mass 60 g moving with a velocity of 10 m/s is approximately (h = 6.63 × 10⁻³⁴ J s)
    1. 10⁻³³ m
    2. 10⁻³¹ m
    3. 10⁻¹⁶ m
    4. 10⁻²⁵ m
  7. A solution of Ba(OH)₂ has a pH of 12.7. What is its molar concentration?
    1. 2.5 × 10⁻² M
    2. 2.5 × 10⁻³ M
    3. 2.5 × 10⁻⁴ M
    4. 2.5 × 10⁻¹ M
  8. Consider the ground state of a chromium atom (Z = 24). The numbers of electrons with azimuthal quantum number l = 1 and l = 2 are respectively
    1. 12 and 4
    2. 12 and 5
    3. 16 and 4
    4. 16 and 5
  9. The number of sulphur atoms in Al₂(SO₄)₃ is
    1. 3
    2. 4
    3. 7
    4. 12
  10. A series of compounds in which successive members of the same group differ by 14 in molar mass (a CH₂ unit) is called a
    1. Alkyl group
    2. Homologous series
    3. Isomerism
    4. All of the above
  11. In the formation of molecular orbitals for diatomic molecules, under which condition does mixing of the s and p atomic orbitals occur?
    1. When the 2s orbitals are ≤ ½ filled
    2. When the 2p orbitals are ≤ ½ filled
    3. When the 2s orbitals are ≥ ½ filled
    4. When the 2p orbitals are ≥ ½ filled
  12. What is the maximum number of electrons in the sub-shell with l = 3 and n = 4?
    1. 10
    2. 12
    3. 14
    4. 16
  13. Choose the correctly balanced equation for the combustion of ethanol.
    1. 2C₂H₅OH + 3O₂ → CO₂ + 3H₂O
    2. C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O
    3. 2C₂H₅OH + 2O₂ → 2CO₂ + 3H₂O
    4. 2C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O
  14. Name the structures (i) (CH₃)₂CHCH₂CHClCH₃ and (ii) CH₃CH₂CHClCHBrCH₃.
    1. (i) 2-chloro-4-methylpentane (ii) 2-bromo-3-chloropentane
    2. (i) 2-chloro-4-methylpentane (ii) 4-bromo-3-chloropentane
    3. (i) 2-methyl-4-chloropentane (ii) 2-bromo-3-chloropentane
    4. None of the above
  15. The electron affinity value (kJ/mol) for O⁻ → O²⁻ is
    1. −142
    2. +702
    3. −60
    4. +820
  16. How many valence electrons appear in the Lewis structure of CH₂Cl₂?
    1. 21
    2. 23
    3. 20
    4. 19
  17. Which of the following bonds is the most polar? (Pauling electronegativities: S 2.58, Se 2.55, Cl 3.16, Br 2.96)
    1. S – Cl
    2. S – Br
    3. Se – Cl
    4. Se – Br
  18. Which type of bond forms between two nonmetal atoms that differ slightly in electronegativity?
    1. Polar covalent
    2. Nonpolar covalent
    3. Ionic
    4. Metallic
  19. A dipole moment
    1. Describes the diatomic formation of two elements
    2. Occurs when all electrons circle the nucleus
    3. Is a measurement of the charge separation in a molecule
    4. Is composed of two polonium isotopes
  20. Ionization energies are determined from
    1. Electrons
    2. Spectra
    3. Geiger–Müller counter
    4. Gas chromatography
  21. Electron affinity is
    1. The amount of energy added to remove an electron from a gaseous atom
    2. The electron affinity of the nucleus
    3. The energy released when an extra electron is added to a neutral gaseous atom
    4. The lanthanide contraction
  22. The Pauling electronegativity coefficients for F and Cl respectively are
    1. 4.0 and 3.0
    2. 5.0 and 4.0
    3. 3.5 and 3.0
    4. None of the above
  23. Which of the following is Fajans' rule?
    1. A small positive ion favours covalency
    2. A small negative ion favours covalency
    3. Polarization is favoured if the positive ion has a noble gas configuration
    4. None of the above
  24. Which of the following compounds is electrovalent (ionic)?
    1. CaCl₂
    2. HCl
    3. NH₃
    4. CH₄
  25. A calcium atom ionizes by
    1. Gaining two electrons
    2. Losing two electrons
    3. Sharing two electrons
    4. Gaining two protons
  26. The energy required to remove the most loosely bound electron from an atom in the gaseous state is known as the
    1. Bond energy
    2. Ionization energy
    3. Activation energy
    4. Mechanical energy
  27. In the formation of NaCl, electron(s) is transferred from the sodium atom to the chlorine atom to form
    1. Na²⁺ and Cl⁻
    2. Na⁺ and Cl²⁻
    3. Na⁺ and Cl⁻
    4. Na⁰ and Cl²⁻
  28. ²⁰Ca → ²⁰Ca²⁺ + 2e⁻. The Ca²⁺ ion has
    1. 18 electrons
    2. 20 electrons
    3. 22 electrons
    4. 122 protons
  29. sp³d² hybridization of a central atom leads to which molecular geometry?
    1. Square planar
    2. Tetrahedral
    3. Trigonal bipyramidal
    4. Octahedral
  30. The overlapping power of hybrid orbitals follows which order?
    1. sp > sp² > sp³
    2. sp < sp² < sp³
    3. sp² > sp > sp³
    4. sp < sp² > sp³
  31. What hybridization change does the carbon atom undergo in the combustion of methane? CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g)
    1. sp → sp²
    2. sp² → sp³
    3. sp³ → sp
    4. sp² → sp
  32. The correct set of quantum numbers for the valence electron of rubidium (Z = 37) is
    1. 5, 0, 0, +½
    2. 5, 1, 0, +½
    3. 5, 1, 1, +½
    4. 6, 0, 0, +½
  33. Neutrons were discovered by
    1. John Dalton
    2. Michael Faraday
    3. J. J. Thomson
    4. James Chadwick
  34. The azimuthal quantum number describes the
    1. Size of an orbital
    2. Shape of an orbital
    3. Orientation of an orbital
    4. Spin of an electron
  35. The development of the cathode ray tube led to the discovery of the
    1. Proton
    2. Electron
    3. Neutron
    4. Positron
  36. Who proposed the wave–particle duality of the electron?
    1. Albert Einstein
    2. Werner Heisenberg
    3. Louis de Broglie
    4. R. A. Millikan
  37. The outermost electronic configuration of the most electronegative element is
    1. ns², np³
    2. ns², np⁴
    3. ns², np⁵
    4. ns², np⁶
  38. Every atomic orbital is described by a set of quantum numbers given as
    1. n, l, mₗ, mₛ
    2. n, mₗ, mₛ
    3. n, l, mₗ
    4. n, l, mₛ
  39. Colligative properties include
    1. Osmotic pressure, vapour pressure lowering, boiling point depression and freezing point depression
    2. Osmotic pressure, vapour pressure lowering, boiling point elevation and freezing point depression
    3. Osmotic pressure, fusion pressure lowering, boiling point depression and freezing point depression
    4. Osmosis, vapour pressure lowering, boiling point depression and freezing point depression
  40. Calculate the freezing point of an antifreeze solution prepared by dissolving 65 cm³ of ethylene glycol (CH₂OHCH₂OH, d = 1.12 g/mL) in 65 g of water. (Kf of water = 1.86 °C kg/mol)
    1. −33.55 °C
    2. −34.48 °C
    3. −33.48 °C
    4. −36.45 °C
  41. The number of moles of a substance in relation to the total moles of the solution is the
    1. Mole ratio
    2. Molecularity
    3. Mole fraction
    4. Mole concept
  42. Which of these homonuclear diatomic molecules does not exist in nature?
    1. Dihydrogen
    2. Di-helium
    3. Di-boron
    4. Dinitrogen
  43. What is the bond order of dinitrogen (N₂)?
    1. 1
    2. 2
    3. 3
    4. 4
  44. Which option matches the molecular orbital configuration of dicarbon (C₂)?
    1. σ1s² σ*1s² σ2s² σ*2s² π2p_y² π2p_z² σ2p_x⁰ σ*2p_x⁰ π*2p_y⁰ π*2p_z⁰
    2. σ1s² σ*1s² σ2s² σ*2s² π2p_y² π2p_z² σ2p_x² σ*2p_x⁰ π*2p_y⁰ π*2p_z⁰
    3. σ1s² σ*1s² σ2s² σ*2s² π2p_y² π2p_z² σ2p_x² σ*2p_x² π*2p_y⁰ π*2p_z⁰
    4. σ1s² σ*1s² σ2s² σ*2s² π2p_y⁰ π2p_z² σ2p_x² σ*2p_x² π*2p_y² π*2p_z⁰
  45. Which of the following homonuclear diatomic molecules does not involve mixing of s and p orbitals in the formation of its molecular orbitals?
    1. B₂
    2. C₂
    3. N₂
    4. O₂
  46. H₃PO₄ + HCO₃⁻ ⇌ H₂PO₄⁻ + H₂CO₃ (K >> 1). The conjugate of HCO₃⁻ is
    1. Acid, H₂CO₃
    2. Acid, CO₃²⁻
    3. Acid, H₃PO₄
    4. Base, H₂CO₃
  47. Which of the following molecules or ions is the strongest acid?
    1. CF₃CO₂H
    2. CF₂HCO₂H
    3. CFH₂CO₂H
    4. CH₃CO₂H
  48. Metathesis reactions are classified as
    1. Precipitation reactions
    2. Double displacement reactions
    3. Neutralization reactions
    4. All of the above
  49. Which of the following is a combustion reaction?
    1. SO₂ + 2NaOH → Na₂SO₃ + H₂O
    2. BaCl₂ + K₂SO₄ → 2KCl + BaSO₄
    3. 2C₄H₁₀ + 13O₂ → 8CO₂ + 10H₂O
    4. Cl₂ + 2NaI → 2NaCl + I₂
  50. When a metal and a nonmetal other than oxygen react, what is formed?
    1. Water
    2. An ionic compound
    3. An elemental compound
    4. None of the above
  51. Which of the following is a precipitation reaction?
    1. AgNO₃ + NaCl → AgCl + NaNO₃
    2. FeS + O₂ → Fe₂O₃ + SO₂
    3. Na₂O + CO₂ → Na₂CO₃
    4. CaO + 2HCl → CaCl₂ + H₂O
  52. What is a net ionic equation?
    1. An equation given so that all ions are shown
    2. An equation that includes only ions
    3. An equation that includes all the substances in the reaction
    4. An equation that includes only the substances that take part in the reaction
  53. For the unbalanced redox reaction Cr₂O₇²⁻(aq) + NO₂⁻(aq) → Cr³⁺(aq) + NO₃⁻(aq), what are the oxidation numbers of Cr in Cr₂O₇²⁻ and of N in NO₂⁻?
    1. +12 and +3
    2. +6 and +3
    3. +6 and −3
    4. +7 and +5
  54. What is the oxidizing agent in the reaction Cr₂O₇²⁻(aq) + NO₂⁻(aq) → Cr³⁺(aq) + NO₃⁻(aq)?
    1. Cr₂O₇²⁻
    2. NO₂⁻
    3. Cr³⁺
    4. NO₃⁻
  55. What is being reduced in the reaction Cr₂O₇²⁻(aq) + NO₂⁻(aq) → Cr³⁺(aq) + NO₃⁻(aq)?
    1. Cr₂O₇²⁻
    2. NO₂⁻
    3. Cr³⁺
    4. NO₃⁻
  56. Which of the following are types of structural isomerism?
    1. Chain
    2. Positional
    3. Functional
    4. All of the above
  57. A carbon atom of an organic compound which has all four of its attachments different is called a
    1. Enantiomer carbon
    2. Chiral carbon
    3. Mirror image carbon
    4. γ-carbon
  58. Calculate the molecular formula of the organic compound whose empirical formula is C₃H₇O and whose molecular weight is 118.
    1. C₆H₄O₂
    2. C₆H₁₄O₂
    3. C₅H₁₄O₂
    4. None of the above
  59. Compounds that have the same atomic sequence (connectivity) but differ only in the spatial relationship of their parts are called
    1. Geometrical isomers
    2. Structural isomers
    3. Constitutional isomers
    4. Stereoisomers
  60. The term enantiomer refers to
    1. Two molecules that are non-mirror images and non-superimposable
    2. Two molecules that are mirror images and superimposable
    3. Two molecules that are mirror images and non-superimposable
    4. Two molecules that are non-mirror images and superimposable
  61. The functional group present in a primary amine is
    1. R–NH₂
    2. R–NH–R
    3. R₃N (a nitrogen bonded to three R groups)
    4. R–CONH₂
  62. What is the IUPAC name of the compound CH₃CH₂CH=CH–C(CH₃)(Br)(OH)?
    1. 5-bromo-5-methylhex-3-en-1-ol
    2. 2-bromohex-3-en-2-ol
    3. 1-bromo-2-methylhex-3-en-1-ol
    4. 1-bromo-4-methylhex-3-en-1-ol
  63. Which of the following are examples of reaction types in organic chemistry?
    1. Substitution
    2. Addition
    3. Elimination
    4. All of the above
  64. An organic compound in which one of the carbon atoms has all its four attachments different is called a ______ compound.
    1. β-carbon
    2. Stereocentre
    3. Chiral
    4. Achiral
  65. The cleavage in an organic reaction in which both bonding electrons become associated with one atom is called
    1. Heterolytic fission
    2. Homolytic fission
    3. Both A and B
    4. None of the above
  66. Calculate the index of hydrogen deficiency (degree of unsaturation) of the compounds C₂H₃N and C₅H₁₀Cl₂ respectively.
    1. 2 and 0
    2. 0 and 2
    3. 0 and 1
    4. None of the above

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