Chemistry Exam Past Questions and Answers | JAMB, WAEC and NECO

Chemistry is the study of the substances that make up matter. It looks at their properties, how they react with each other, and how these reactions can create new substances.

• Question 731: The correct order of increasing oxidation number of the transition metal ions for the compounds K₂Cr₂O₇, V₂O₅ and KMnO₄ is Options:
  A) V₂O₅< K_2Cr2O₇< KMnO₄
  B) K₂Cr₂O₇< KMnO_{4 < V2O5}
  C) KMnO₄< K_2Cr2O₇< V_2O5
  D) KMnO₄< V_2O5< K_2Cr2O₇
  Show Answer
  The correct answer is A .
• Question 732: Which of the following compounds is the best possible anti-knock agent for petrol? Options:
  A) (CH₃)₂CH - CH(CH₃)CH₂CH₃
  B) CH₃CH₂(CH₃)CHCH₂CH₂CH₃
  C) CH₃CH₂(CH₃)CHCH₂CH₂CH₃
  D) (CH₃)₃C - CH₂CH₂CH₃
  Show Answer
  The correct answer is A .
• Question 733:

  Chlorine, consisting of two isotopes of mass numbers 35 and 37, has an atomic mass of 35.5.
  The relative abundance of the isotope of mass number 37 is?

  Options:
  A) 20
  B) 25
  C) 50
  D) 75
  Show Answer
  The correct answer is B .
• Question 734:

  Which of the following compounds is an example of an electrovalent bond?

  Options:
  A) NaCl (sodium chloride)
  B) CO2 (carbon dioxide)
  C) H2O (water)
  D) CH4 (methane)
  Show Answer
  The correct answer is A .
• Question 735: In the chemical reaction A + B $\to$ C + D, more of D is formed? Options:
  A) if the concentrated of A is reduced
  B) if the concentrated of B is reduced
  C) if the concentrated of C is reduced
  D) if the concentration of C is increased
  E) if D is continuously removed from the reaction mixture
  Show Answer
  The correct answer is E .
• Question 736:

  Cr₂O$\frac{2-}{7}$ (aq) + H₂O(1)⇌ 2CrO $\frac{2-}{4}$ (aq) + 2H ⁺ (aq)

  What happens to the reaction above when the hydrogen ion concentration is increased?

  Options:
  A) more of the products will be formed
  B) the reaction will not proceed
  C) the equilibrium position will shift to the right
  D) the equilibrium position will shift to the left.
  Show Answer
  The correct answer is D .
• Question 737: A piece of burning sulphur will continue to burn in a gas jar of oxygen to give misty fumes which readily dissolved in water. The resulting liquid is Options:
  A) sulphur (VI) trioxide
  B) tetraoxosulphate (VI) acid
  C) trioxosulphate (IV) acid
  D) dioxosulphate (II) acid
  E) hydrogen sulphide
  Show Answer
  The correct answer is C .
• Question 738: In an equilibrium reaction, which of the following conditions indicates that maximum yield of the product will be obtained? Options:
  A) Equilibrium constant is very large
  B) ∆H - T∆S = O
  C) ∆ H > T ∆ S
  D) Equilibrium constant is less than zero
  Show Answer
  The correct answer is A .
• Question 739: If 100cm³ of oxygen pass through a porous plug is 50 seconds, the time taken for the same volume of hydrogen to pass through the same porous plug is? [O = 16, H = 1] Options:
  A) 10.0s
  B) 12.5s
  C) 17.7s
  D) 32.0s
  Show Answer
  The correct answer is B .
• Question 740: A concentrated solution containing H⁺, Cu²⁺,OH^- and CI^- was electrolysed using platiunm electrodes which of the ions will be discharged at the cathods? Options:
  A) H⁺
  B) Cu²⁺
  C) OH^-
  D) CI^-
  Show Answer
  The correct answer is B .