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 41: 10cm³ of hydrogen fluoride gas react with 5cm³ of dinitrogen difluoride gas (N²F₂) to form 10₃ of a single gas. Which of the following is the most likely equation of the reaction? Options:
  A) HF + N₂F₂ $\to$ N₂HF₃
  B) 2HF + N₂F₂ $\to$ 2NHF₂
  C) 2HF + N₂F₂ $\to$ N₂H₂F₃
  D) HF + 2N₂F₂ $\to$ N₄HF₂
  Show Answer
  The correct answer is B .
• Question 42: The final product of the reaction of ethyne with hydrogen iodine is? Options:
  A) CH₃—CHI₂
  B) CH₂l—CH₂I
  C) CH₃—CI₃
  D) CH₂ = CHI
  Show Answer
  The correct answer is A .
• Question 43: Which of the following salts will turn blue litmus red? Options:
  A) Sodium tetrahydroxozincate (ll)
  B) Potassium hydrogentetraoxosulphate (lV)
  C) Sodium trioxocarbonate (lV)
  D) Zinc chloride hydroxide
  Show Answer
  The correct answer is B .
• Question 44:

  

  The above orbital diagram shown the electronic configuration of

  Options:
  A) chlorine
  B) nitrogen
  C) calcium
  D) neon
  Show Answer
  The correct answer is B .
• Question 45: The bond which joins two ethanoic acid molecules in the liquid state is Options:
  A) a covalent bond
  B) an ionic bond
  C) a dative covalent bond
  D) a hydrogen bond
  Show Answer
  The correct answer is D .
• Question 46:

  Consider the reaction: A + 2B${}_{(g)}\rightleftharpoons$ 2C + D${}_{(g)}$ ($\mathrm{\Delta }$H = +ve)

  What will be the effect of decrease in temperature on the reaction?

  Options:
  A) Rate of backward reaction will increase
  B) The equilibrium constant will shift
  C) Rates of forward and backward reactions are not affected
  D) Rate of forward reaction will increase
  Show Answer
  The correct answer is A .
• Question 47: The ores that can be concentrated by flotation are Options:
  A) nitride ores
  B) sulphide ores
  C) oxide ores
  D) non-metals
  Show Answer
  The correct answer is B .
• Question 48:

  Which of the following reactions would be expected to have the highest entropy change?

  Options:
  A) Liquid → Gas
  B) Solid → Liquid
  C) Gas → Liquid
  D) Gas → Solid
  Show Answer
  The correct answer is A .
• Question 49:

  Which of the following is an example of a chemical change?

  Options:
  A) dissolution of salt in water
  B) rusting of iron
  C) melting of ice
  D) separating a mixture by distillation
  Show Answer
  The correct answer is B .
• Question 50:

  If 30cm³ of oxygen diffuses through a porous pot in 7 seconds, how long will it take 60cm³ of chlorine to diffuse through the same pot, if the vapour densities of oxygen and chlorine are 16 and 36 respectively?

  Options:
  A) 9.3 sec
  B) 14 sec
  C) 21 sec
  D) 28 sec
  E) 30.3 sec
  Show Answer
  The correct answer is C .