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 681:

  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 682: The densities of two gases, X and Y are 0.5gdm^-3 and 2.0gdm^-3 respectively. What is the rate of diffusion of X relative to Y? Options:
  A) 0.1
  B) 0.5
  C) 2.0
  D) 4.0
  Show Answer
  The correct answer is C .
• Question 683: The pollutant that contributes to the depletion of the ozone layer is Options:
  A) CFCs
  B) NO₂
  C) SO₂
  D) CO
  Show Answer
  The correct answer is A .
• Question 684: An example of a solid emulsion is Options:
  A) Butter
  B) Hair cream
  C) Milk
  D) Cod-liver oil
  Show Answer
  The correct answer is A .
• Question 685:

  The number of molecules of Carbon(iv)Oxide produced when 10.0g of CaCO${}_3$ is treated with 0.2dm${}^3$ of 1 Mole of HCL in the equation

  CaCO${}_3$ + 2HCL $\to$ CaCl${}_2$  + H${}_2$ O + CO${}_2$  , is ?

  Options:
  A) 1.00 X 10${}^{23}$
  B) 6.02 X 10${}^{23}$
  C) 6.02 X 10${}^{22}$
  D) 6.02 X 10${}^{24}$
  Show Answer
  The correct answer is C .
• Question 686: The oxidation state of oxygen in tetraoxosulphate (VI) acid is Options:
  A) -4
  B) -2
  C) +4
  D) -8
  Show Answer
  The correct answer is B .
• Question 687: What is observed when aqueous solutions of each of tetraoxosulphate (VI) acid, potassium trioxoiodate (V) and potassium iodide are mixed together? Options:
  A) A white precipitate is formed
  B) A green precipitate is formed
  C) The mixture remains colourless
  D) The mixture turns reddish brown
  Show Answer
  The correct answer is D .
• Question 688: All these are electromagnetic waves except Options:
  A) White light
  B) Photon
  C) X-ray
  D) Infrared
  Show Answer
  The correct answer is B .
• Question 689: The leachate of a certain plant ash is used in local soap making because it contains Options:
  A) sodium chloride and potassium hydroxide
  B) sodium hydroxide
  C) potassium hydroxide
  D) soluble carbonates and hydrogen carbonates
  Show Answer
  The correct answer is B .
• Question 690: Alkanols have the general molecular formula Options:
  A) C₁H_2n-2
  B) C₁H_2n-1CHO
  C) C₁H_2n-2OH
  D) C₂H_2n+1OH
  Show Answer
  The correct answer is D .