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 781: In a flame test for calcium, the flame appears Options:
  A) green when viewed through a blue glass
  B) blue when viewed through a blue glass
  C) orange -red when viewed through a blue glass
  D) brick-red when viewed through a blue-glass
  Show Answer
  The correct answer is D .
• Question 782: Inspite of the electronic configuration, 1s²2s²2p², carbon is tetraavalent because? Options:
  A) the electrons in both 2s and 2p orbitals have equal energy
  B) the electrons in both 2s and 2p orbitals are equivalent
  C) both the 2s and 2p orbitals hybridizes
  D) the six orbitals hybridize to four
  Show Answer
  The correct answer is C .
• Question 783: The principal constituent of natural gas is Options:
  A) methane
  B) ethane
  C) propane
  D) Butane
  Show Answer
  The correct answer is A .
• Question 784: Which of the following gases is the most dangerous pollutant? Options:
  A) Hydrogen sulphide
  B) Carbon (lV) oxide
  C) Sulphur (lV) oxide
  D) Carbon (ll) oxide
  Show Answer
  The correct answer is D .
• Question 785: In the chemical reaction A + B $\to$ C + D, more of D is formed? Options:
  A) if the concentrated of A is reduced
  B) if the concentrated of B is reduced
  C) if the concentrated of C is reduced
  D) if the concentration of C is increased
  E) if D is continuously removed from the reaction mixture
  Show Answer
  The correct answer is E .
• Question 786: The molecular lattice of iodine is held together by Options:
  A) dative bond
  B) metallic bond
  C) hydrogen bond
  D) van der Waal's forces
  Show Answer
  The correct answer is D .
• Question 787:

  Elements X and Y have electronic configurations 1s${}^2$2s${}^2$2p${}^4$ and 1s${}^2$2s${}^2$2p${}^6$3s${}^2$3p${}^1$ respectively. When they combine, the formula of the compound formed is

  Options:
  A) XY
  B) X${}_2$Y
  C) Y${}_2$X${}_3$
  D) X${}_2$Y${}_3$
  Show Answer
  The correct answer is C .
• Question 788: A few drops of NaOH solution was added to an unknown salt forming a white precipitate which is insoluble in excess solution. The cation likely present is Options:
  A) Zn²⁺
  B) Pb²⁺
  C) Ca²⁺
  D) Al³⁺
  Show Answer
  The correct answer is C .
• Question 789:

  The enzyme that converts glucose to ethylalcohol is?

  Options:
  A) maltase
  B) zymase
  C) Diatase
  D) Invertase
  Show Answer
  The correct answer is B .
• Question 790: In the industrial production of hydrogen from natural gas, carbon (IV) oxide produced along with the hydrogen is removed by? Options:
  A) washing under pressure
  B) passing the mixture into lime water
  C) using ammoniacal copper (l) chloride
  D) drying over phoshorus (V) oxide
  Show Answer
  The correct answer is C .