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 1431: The number of electrons in the valence shell of an element of atomic number 14 is? Options:
  A) 1
  B) 2
  C) 3
  D) 4
  Show Answer
  The correct answer is D .
• Question 1432:

  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 1433: Which of the following molecules is held together by hydrogen bond? Options:
  A) CH₄
  B) HBr
  C) H₂SO₄
  D) HF
  Show Answer
  The correct answer is D .
• Question 1434: 9.8g of solid potassium chlorate (KCIO₃) were added to 40 cm³ of water and heated to dissolve all the solid. As he solution cooled, crystals of potassium chlorate started forming at 60°C. The solubility of potassium chlorate at 66°C is therefore? Options:
  A) 24.5 mole per dm³
  B) 0.2 mole per dm³
  C) 10.0 mole per dm³
  D) 20.0 mole per dm³
  E) 2.0 mole per dm³
  Show Answer
  The correct answer is E .
• Question 1435:

  

  The solubility curves of four substances are shown in the figure above. Which of the four substances would crystallize from a saturated solution cooled from 353K(80^oC)to 323K(50C)?

  Options:
  A) P and Q
  B) P and R
  C) P and S
  D) R and S
  E) Q and R
  Show Answer
  The correct answer is D .
• Question 1436: 0.25 mole of hydrogen chloride was dissolved in distilled water and the volume made up of 0.50 dm³. If 15.0 cm³ of the solution requires 12.50 cm³ of aqueous sodium trioxocarbonate (IV) for neutralization, calculate the concentration of the alkaline solution Options:
  A) 0.30 mol dm³
  B) 0.40 mol dm³
  C) 0.50 mol dm³
  D) 0.60 mol dm³
  Show Answer
  The correct answer is A .
• Question 1437: In the electrolysis of a concentrated solution of sodium chloride using electrodes, which of the following ions are discharged at the cathode and anode respectively? Options:
  A) Na⁺ and Cl^-
  B) Na⁺ and OH^-
  C) H⁺ and OH^-
  D) H⁺ and Cl^-
  Show Answer
  The correct answer is D .
• Question 1438: Which of the following organic compounds is very soluble in water? Options:
  A) CH₃COOH
  B) C₂H₂
  C) C₂H₄
  D) CH₃COOC₂H₅
  Show Answer
  The correct answer is A .
• Question 1439: Methanoic acid mixes with water in all proportions and has about the same boiling point as water which of the following methods would you adopt to obtain pure water from a mixture of stand, water and methanoic acid? Options:
  A) fractional distillation
  B) filtration followed by distillation
  C) neutralization with sodium hydroxide followed by distillation
  D) esterification with ethanol followed by distillation
  E) neutralization with sodium hydroxide followed by filtration
  Show Answer
  The correct answer is B .
• Question 1440: 50 cm³ of carbon (II) oxide was exploded with 150 cm³ of air containing 20% oxygen by volume. Which of the reactants was in excess? Options:
  A) Carbon (II) oxide
  B) Carbon (IV) oxide
  C) Oxygen
  D) Nitrogen
  Show Answer
  The correct answer is C .