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 2071: Which of the following is a example of a chemical change? Options:
  A) Dissoultion 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 2072:

  NH₃ + H₃O⁺

  → NH₄⁺ + H₂O. It may be deduced from the reaction above that?

  Options:
  A) a redox reaction has occurred
  B) H₃O⁺ acts as an oxidizing agent
  C) H₃O⁺ acts as an acid
  D) water acts as ab acid
  Show Answer
  The correct answer is C .
• Question 2073: The mixture of gases used in a photographer's flash tube is Options:
  A) argon and krypton
  B) krypton and xenon
  C) helium and argon
  D) argon and xenon
  Show Answer
  The correct answer is B .
• Question 2074:

  n monosaccharide $\underset{Q}{\stackrel{P}{\rightleftharpoons }}$ polysaccharide -n water.

  In the process above, P and Q respectively represent

  Options:
  A) Condensation and hydrolysis
  B) Fermentation and condensation
  C) Polymerization and hydrolysis
  D) Polymerization and condensation
  Show Answer
  The correct answer is A .
• Question 2075:

  

  The tabulated results below were obtained by titration 10.0 cm³ of water with soup. The titration was repeated with the same sample of water after boiling. The ratio of permanent to temporary hardness is

  Options:
  A) 1.5
  B) 1.4
  C) 4.1
  D) 5.1
  Show Answer
  The correct answer is C .
• Question 2076: Which of the following combination of gases is used for metal welding? i. Oxygen and ethyne, ii. Hydrogen and ethyne, iii. Hydrogen and oxygen, iv. Ethyne, hydrogen and oxygen. Options:
  A) i and ii
  B) ii and iv
  C) i and iii
  D) ii and iv
  Show Answer
  The correct answer is A .
• Question 2077: How many electrons are in the L shell of ³¹₁₅P? Options:
  A) 5
  B) 8
  C) 18
  D) 2
  Show Answer
  The correct answer is B .
• Question 2078: Given the mean atomic mass of chlorine prepared in the laboratory to be 35.5 and assuming that chlorine contains two isotopes of mass number 35 nad 37, what is the percentage composition of the isotope of mass number 35? Options:
  A) 20
  B) 25
  C) 50
  D) 75
  E) 90
  Show Answer
  The correct answer is D .
• Question 2079: Which of the following statements about phosphorus is NOT correct? Options:
  A) Phosphorus is a solid mineral
  B) Phosphorus is obtained by oxidation reaction of phosphate
  C) Phosphorus exists in two allotropic forms
  D) Both forms of phosphorus are interconvertible
  E) Yellow phosporus ignites when rubbed on a rough surface
  Show Answer
  The correct answer is E .
• Question 2080:

  The salt that reacts with dilute hydrochloric acid to produce a pungent smelling gas which decolourizes acidified purple potassium tetraoxomanganate (VII) solution is

  Options:
  A) Na${}_2$SO${}_4$
  B) Na${}_2$SO${}_3$
  C) Na${}_2$S
  D) Na${}_2$CO${}_3$
  Show Answer
  The correct answer is B .