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 491: Which of the following statement is correct about the periodic table? Options:
  A) Elements in the same period have the same number of valency electron
  B) The valence electron of the elements in the same period increase progressively across the period
  C) Elements in the same group have the same number of electron shells
  D) The non-metallic properties of the elements tend to decrease across each period
  Show Answer
  The correct answer is B .
• Question 492:

  3Cu + pHNO₃ →3Cu(NO)₂ + 4H₂ O + xNO

  In the equation above, the values of p and x respectively are

  Options:
  A) 1 and 3
  B) 2 and 3
  C) 6 and 2
  D) 8 and 2
  Show Answer
  The correct answer is D .
• Question 493:

  Which of the following salts when dissolved in water will NOT give the corresponding pH value?

  Options:
  A) NaHSO₄, pH < 5
  B) Na₂CO₃, pH > 8
  C) Na₂Cl,pH = 7
  D) NaHCO, pH < 6
  Show Answer
  The correct answer is D .
• Question 494: The process involved in the conversion of an oil into margarine is known as? Options:
  A) hydrogenation
  B) condensation
  C) pyrolysis
  D) dehydration
  E) cracking
  Show Answer
  The correct answer is A .
• Question 495: The relationship between the velocity (U) of gas molecules and their relative molecular mass (M) is shown by the equation Options:
  A) U = (kM)$\frac{1}{2}$
  B) U = (kM)²
  C) U = $\sqrt{k}m$
  D) U = ($\frac{k}{m}$)${}^{\frac{1}{2}}$
  Show Answer
  The correct answer is C .
• Question 496: Hydrogen diffuses through a porous plug Options:
  A) at the same rate as oxygen
  B) at a slower rate than oxygen
  C) twice as fast as oxygen
  D) three times as fast as oxygen
  E) four times as fast as oxygen
  Show Answer
  The correct answer is E .
• Question 497: In the extraction of iron, the waste gas from the furnace is a mixture of Options:
  A) PH₃ CO and CO₂
  B) CO and C
  C) N₂ CO and CO₂
  D) PH₃ and CO
  Show Answer
  The correct answer is A .
• Question 498: The substance that is used in the steel industry for the removal of carbon. Sulphur and phosphorus impurities from pig iron is Options:
  A) oxygen
  B) chlorine
  C) nitrogen
  D) hydrogen
  Show Answer
  The correct answer is A .
• Question 499: The colour imparted to a flame by calcuium ion is Options:
  A) green
  B) blue
  C) brick-red
  D) yellow
  E) lilac
  Show Answer
  The correct answer is C .
• Question 500: Hydrogen is not liberated when trioxonitrate(v)acid reacts with zinc because Options:
  A) zinx is not rendered passive by acid
  B) hydrogen produced is oxidized to water
  C) oxides of nitrogen are produced
  D) all nitrates are soluble in water
  E) trioxonitrate(v)acid is a strong acid
  Show Answer
  The correct answer is E .