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 1: When a solution of ammonium trioxocarbonate (IV) is added to a solution of an unknown salt, a white precipitate which is soluble in dilute hydrochloric acid but insoluble in ethanoic acid is formed. This indicates the presence of Options:
  A) Ca²⁺
  B) Na⁺
  C) Zn²⁺
  D) K⁺
  Show Answer
  The correct answer is A .
• Question 2: Which of the following statements is true? When the potassium atom forms its ion Options:
  A) it gains one electron and becomes neutral
  B) its atomic number decreases
  C) it achieves electronic configuration of orgon
  D) it loses one proton
  E) it loses one neutron
  Show Answer
  The correct answer is C .
• Question 3: The standard enthalpies of formation of CO_2(g), H₂O(g) and CO_(g) in kJ mol^- are -394, -242 and -110 respectively. What is the standard enthalpy change for the reaction CO_(g) + H_2(g)O → CO_2(g) + H_2(g)? Options:
  A) -42 KJ mol^-
  B) +42 KJ mol^-
  C) -262 KJ mol^-
  D) +262 KJ mol^-
  Show Answer
  The correct answer is A .
• Question 4: The shape of the hydrocarbon compound CH₄ is Options:
  A) square planar
  B) planar
  C) linear
  D) tetrahedral
  Show Answer
  The correct answer is D .
• Question 5: Which of the following happens during the electrolysis of molten sodium chloride? Options:
  A) Sodium ion loses an electron
  B) Chlorine atom gains an electron
  C) Chlorine ion gains an electron
  D) Sodium ion is oxidized
  E) Chloride ion is oxidized
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  The correct answer is E .
• Question 6:

  A compound contains 31.91% potassium, 28.93% chlorine and the rest oxygen. What is the chemical formula of the compound?

  [K = 39, Cl = 35.5, O = 16]

  Options:
  A) KClO₄
  B) KClO
  C) KClO₂
  D) KClO₃
  Show Answer
  The correct answer is D .
• Question 7:

  A solution X, on mixing with AgNO${}_3$ solution gives a white precipitate soluble in aqueous NH${}_3$, a solution Y, when also added to X, also gives a white precipitate which is soluble when heated solutions X and Y respectively contain

  Options:
  A) Al${}^{3+}$, Cl${}^{-}$
  B) Hg${}^{+}$, SO${}_4^{2-}$
  C) Pb${}^{2+}$, Cl${}^{-}$
  D) Ag${}^{+}$, SO${}_4^{2-}$
  Show Answer
  The correct answer is C .
• Question 8: Which of the following is a neutralization reaction? Addition of Options:
  A) nitric acid to hydrochloric acid
  B) nitric acid to sulphuric acid
  C) nitric acid to distilled water
  D) nitric acid to sodium hydroxide
  E) sodium chloride to distilled water
  Show Answer
  The correct answer is D .
• Question 9: If 48,000 coulombs of electricity are required to discharge 0.5 mole of sodium from a molten sodium chloride mass, then the number of coulombs required to discharge 2 moles of lead from molten lead (ll) chloride is? Options:
  A) 48,000
  B) 96,000
  C) 192,000
  D) 384,000
  E) 576,000
  Show Answer
  The correct answer is D .
• Question 10: The noble gas, argon,is used for Options:
  A) electric arc welding
  B) welding brass
  C) underwater welding
  D) steel welding
  Show Answer
  The correct answer is A .