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 251: When salt loses its water of crystallization to the atmosphere on exposure, the process is said to be Options:
  A) efflorescence
  B) déliquescence
  C) effervescence
  D) fluorescence
  Show Answer
  The correct answer is A .
• Question 252: The pH of a solution obtained by mixing 100cm³ of a 0.2M solution of NaOH is? Options:
  A) 1.3
  B) 7.0
  C) 9.7
  D) 12.7
  Show Answer
  The correct answer is D .
• Question 253: 2SO_2(g) + O_2(g) ↔ 2SO_3(g). In the chemical reaction above, the substance that will increase the rate of production of sulphur (VI) oxide is Options:
  A) manganese (IV) oxide
  B) finely divided iron
  C) vanadium (V) oxide
  D) nickel
  Show Answer
  The correct answer is C .
• Question 254:

  HCL_(aq) + H₂O_(l) H₃O⁺_(aq) + Cl^-_(aq)

  In the reaction above, Cl^-_(aq) is the

  Options:
  A) conjugate acid
  B) acid
  C) conjugate base
  D) base
  Show Answer
  The correct answer is C .
• Question 255: Which of the following gases contains the least number of atoms at s.t.p? Options:
  A) 1 mole of butane
  B) 3 mole of ozone
  C) 4 mole of chlorine
  D) 7 mole of argon
  Show Answer
  The correct answer is A .
• Question 256:

  Given that 15.00 cm³ of H₂

  SO₄ was required to completely neutralize 25.00 cm³ of 0.125 mol dm^-3 NaOH, calculate the molar concentration of the acid solution:

  Options:
  A) 0.925 mol dm^-3
  B) 0.156mol dm^-3
  C) 0.104 mol dm^-3
  D) 0.023 mol dm^-3
  Show Answer
  The correct answer is C .
• Question 257: The volume of a given gas is V cm³P mm Hg. what is the new volume of the gas if the pressure is reduced to half at constant temperature Options:
  A) 4 V cm³
  B) 2 V cm³
  C) V/2 cm³
  D) V cm³
  Show Answer
  The correct answer is B .
• Question 258: The tincture of iodine means iodine dissolved in Options:
  A) ethanol
  B) bromine chloride
  C) chlorine water
  D) water
  Show Answer
  The correct answer is A .
• Question 259: Which of the following compounds is NOT formed by the action of chlorine on methane? Options:
  A) CH₃CI
  B) C₂H₅CI
  C) CH₂CI₂
  D) CHCI₃
  Show Answer
  The correct answer is B .
• Question 260: The oxidation number of manganese in KMnO₄ is? Options:
  A) +1
  B) +3
  C) +5
  D) +7
  E) +2
  Show Answer
  The correct answer is D .