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 1851:

  Four elements P, Q, R and S have atomic numbers of 4, 10, 12 and 14 respectively. Which of these elements is noble gas? 

  Options:
  A) P
  B) Q
  C) R
  D) S
  Show Answer
  The correct answer is B .
• Question 1852: Phosphorus is stored under water to prevent it from Options:
  A) Dehydrating
  B) Becoming inert
  C) Smelling
  D) Catching fire
  Show Answer
  The correct answer is D .
• Question 1853:

  NO_(g) + CO_(g) ↔ (1)/(2)N_2(g) + CO_2(g) ∆H = -89.3 kj.

  What conditions would favour maximum conversion of nitrogen (II) oxide and carbon (II) oxide in the reaction above?

  Options:
  A) Low temperature and high pressure
  B) High temperature and low pressure
  C) High temperature and high pressure
  D) Low temperature and low pressure
  Show Answer
  The correct answer is A .
• Question 1854: If an element X of an atomic number Z and mass number Y is irradiated by an intense concentration of neutrons, the relevant nuclear equation is? Options:
  A) ^y_zX + ¹₀n → ^{y - 1}_{z + 1}X
  B) ^y_zX + ¹₀n → ^{y + 1}_zX
  C) ^y_zX + ¹₀n → ^y_{z + 1}X
  D) ^y_zX + ¹₀n → ^{y + 1}_{z - 1}X
  Show Answer
  The correct answer is B .
• Question 1855:

  When cathode rays are deflected onto the electrode of an electrometer, the instrument becomes?

  Options:
  A) Bipolar
  B) Negatively charged
  C) Positively charged
  D) Neutral
  Show Answer
  The correct answer is B .
• Question 1856: A quantity of air was passed through a weighed amount of alkaline pyrogallol. An increase in the weight of the pyrogallol would result from the absorption of? Options:
  A) nitrogen
  B) neon
  C) argon
  D) oxygen
  Show Answer
  The correct answer is D .
• Question 1857: An acid and its conjugate base Options:
  A) can neutralise each other to form a salt
  B) differ only by a proton
  C) differ only by the opposite charges they carry
  D) are always neutral substances
  Show Answer
  The correct answer is B .
• Question 1858: Which of the following is physical change? Options:
  A) Burning kerosene
  B) Freezing ice cream
  C) Exposing white phosphorus
  D) Dissolving calcium in water
  Show Answer
  The correct answer is B .
• Question 1859: Clothes should be properly rinsed with water after bleaching because? Options:
  A) the bleach decolourizes the cothes
  B) chlorine reacts with fabrics during bleaching
  C) the clothes are sterilized during bleaching
  D) hydrogen chloride solution is produced during bleaching
  Show Answer
  The correct answer is D .
• Question 1860: In an equilibrium reaction, which of the following conditions indicates that maximum yield of the product will be obtained? Options:
  A) Equilibrium constant is very large
  B) ∆H - T∆S = O
  C) ∆ H > T ∆ S
  D) Equilibrium constant is less than zero
  Show Answer
  The correct answer is A .