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 2281: Which of the following compounds gives a yellow residue when heated and also reacts with aqueous sodium hydroxide to give a white gelatinous precipitate soluble in excess sodium hydroxide solution? Options:
  A) (NH₄)CO₃
  B) ZnCO₃
  C) Al₂(SO₄)₃
  D) PbCO3
  Show Answer
  The correct answer is B .
• Question 2282:

  In the upper atmosphere, the ultra-violet light breaks off a free chlorine atom from chlorofluorocarbon molecule. The effect of this is that the free chlorine atom will

  Options:
  A) be very reactive and will attack ozone
  B) be non-reactive and will not attack ozone
  C) not change the level of ozone in the atmosphere
  D) increase the level of ozone in the atmosphere
  Show Answer
  The correct answer is A .
• Question 2283: In the electrolytic extraction of aluminum, the function of the molten cryolite is to Options:
  A) precipitate aluminium hdroxide
  B) lower the melting point of aluminium oxide
  C) act as a raw materials
  D) act as a solvent
  Show Answer
  The correct answer is B .
• Question 2284:

  Which of the following conditions will most enhance the spontaneity of a reaction?

  Options:
  A) $\mathrm{\Delta }$H is negative and greater than T$\mathrm{\Delta }$S
  B) $\mathrm{\Delta }$H is negative and $\mathrm{\Delta }$S = 0
  C) $\mathrm{\Delta }$H is positive and less than T$\mathrm{\Delta }$S
  D) $\mathrm{\Delta }$H is positive and equal to T$\mathrm{\Delta }$S
  Show Answer
  The correct answer is A .
• Question 2285: Which of the following are the products of the reaction between CH₃COOH and CI₂ in sunlight? Options:
  A) CICH₂COOH + HCI
  B) CH₃COCI + HOCI
  C) CH₃COOCI + HCI
  D) CH₃COCI + HO₂
  Show Answer
  The correct answer is A .
• Question 2286: The presence of an impurity in substance will cause the melting point to Options:
  A) be zero
  B) reduce
  C) increase
  D) be stable
  Show Answer
  The correct answer is B .
• Question 2287:

  A gaseous metallic chloride MCl consists of 20.22% of M by mass. The formula of the chloride is?

  [ M = 27, Cl = 35.5]

  Options:
  A) MCl
  B) MCl${}_2$
  C) MCl${}_3$
  D) M${}_2$Cl${}_6$
  Show Answer
  The correct answer is C .
• Question 2288: An isotope has an atomic number of 17 and a mass number of 36. Which of the following gives the correct number of neutrons and protons in an atom of the isotope? Options:
  A) Neutrons 53, Protons 17
  B) Neutrons 17, Protons 36
  C) Neutrons 19, Protons 17
  D) Neutrons 36, Protons 17
  Show Answer
  The correct answer is C .
• Question 2289: Steam changes the colour of anhydrous cobalt (ll) chloride from Options:
  A) white to red
  B) blue to white
  C) blue to pink
  D) white to blue
  Show Answer
  The correct answer is C .
• Question 2290:

  

  Use the following option above to answer this question. Which of the following is the functional group of carboxylic acids?

  Options:
  A) A
  B) B
  C) C
  D) D
  E) E
  Show Answer
  The correct answer is D .