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 1991:

  Addition of sodium chloride to water to form a solution would lead to?

  Options:
  A) increase in freezing point and increase the boiling point
  B) increase in freezing point and decrease the boiling point
  C) decrease in freezing point and decrease the boiling point
  D) decrease in freezing point and increase the boiling point
  Show Answer
  The correct answer is D .
• Question 1992:

  A solution X, on mixing with AgNO${}_3$ solution gives a white precipitate soluble in aqueous NH${}_3$, a solution Y, when also added to X, also gives a white precipitate which is soluble when heated solutions X and Y respectively contain

  Options:
  A) Al${}^{3+}$, Cl${}^{-}$
  B) Hg${}^{+}$, SO${}_4^{2-}$
  C) Pb${}^{2+}$, Cl${}^{-}$
  D) Ag${}^{+}$, SO${}_4^{2-}$
  Show Answer
  The correct answer is C .
• Question 1993: The most suitable metal that can be used as lightning conductor is Options:
  A) silver
  B) copper
  C) iron
  D) aluminium
  Show Answer
  The correct answer is B .
• Question 1994: Water for town supply is chlorinate to make it free from Options:
  A) bad colour
  B) bacteria
  C) temporary hardness
  D) permanent hardness
  Show Answer
  The correct answer is B .
• Question 1995: When H₂S gas is passed into a solution of iron (III) chloride, the colour changes from yellow to green. This is because? Options:
  A) H_(s)S is reduced to S
  B) Fe³⁺ ions are oxidized by H_(s)S
  C) Fe³⁺ ions are oxidized Fe³⁺ ions
  D) Fe³⁺ ions are reduced to Fe²⁺ ions
  Show Answer
  The correct answer is D .
• Question 1996: Three drops of a 1.0 mol dm^-3 solution of HCl was added to 20 cm³ of a solution of pH6.4. The pH of the resulting solution will be Options:
  A) close to that of pure water
  B) less than 6.4
  C) greater than 6.4
  D) unaltered
  Show Answer
  The correct answer is B .
• Question 1997:

  The general formula for the Alkanals is?

  Options:
  A) R${}_2$CO
  B) RCHO
  C) ROH
  D) RCOOR
  Show Answer
  The correct answer is B .
• Question 1998: Helium is often used in observation balloons because it is? Options:
  A) light and combustible
  B) light and non-combustible
  C) heavy and combustible
  D) heavy and non-combustible
  Show Answer
  The correct answer is B .
• Question 1999: Rare gases are suitable because they Options:
  A) are monoatomic
  B) form ions easily
  C) have duplet or octet electronic configuration in the outermost shells in their atoms
  D) are volatile gases
  Show Answer
  The correct answer is C .
• Question 2000:

  CH₃-CH-CH₃

  CH₂CI Is known as?

  Options:
  A) 1-chloro-2-methylbutane
  B) 1-chloro-2-methylpropane
  C) 2-chloromethylpropane
  D) 1-chloro-2, 2-dimethylethane
  Show Answer
  The correct answer is B .