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 241: The process of converting linear alkanes to branched chain and cyclic hydrocarbons by heating in the presence of a catalyst to improve the quality of petrol is referred to as Options:
  A) refining
  B) craching
  C) reforming
  D) blending
  Show Answer
  The correct answer is C .
• Question 242: How many isomers does pentane have? Options:
  A) 6
  B) 5
  C) 4
  D) 3
  Show Answer
  The correct answer is D .
• Question 243: How many moles of HCl will be required to react with potassium heptaoxodichromate (VI) to produce 3 moles of chlorine? Options:
  A) 14
  B) 12
  C) 11
  D) 10
  Show Answer
  The correct answer is A .
• Question 244:

  Which of the following is an example of an endothermic reaction?

  Options:
  A) Combustion of propane (C${}_3$H${}_8$) to produce carbon dioxide (CO${}_2$) and water (H${}_2$O).
  B) Burning of methane (CH${}_4$) in the presence of oxygen
  C) Formation of table salt (NaCl) from sodium (Na) and chlorine (Cl${}_2$).
  D) Decomposition of hydrogen peroxide (H${}_2$O${}_2$) into water (H${}_2$O) and oxygen (O${}_2$).
  Show Answer
  The correct answer is D .
• Question 245: The electron configuration of ₂₂X ²⁺ ion is Options:
  A) 1s² 2s²2p⁶ 3s² 3p⁶ 4s² 3d²
  B) 1s² 2s²2p⁶ 3s² 3p⁶ 4s² 3d¹
  C) 1s² 2s²2p⁶ 3s² 3p⁶
  D) 1s² 2s²2p⁶ 3s² 3p⁶ 4s²
  Show Answer
  The correct answer is D .
• Question 246:

  How many atoms are present in 6.0g of magnesium?

  [Mg = 24, N_A = 6.02 x 10²³ mol^-1]

  Options:
  A) 1.20 x 10²²
  B) 2.41 x 10²²
  C) 1.51 x 10²³
  D) 3.02 x 10²³
  Show Answer
  The correct answer is C .
• Question 247:

  A chemical widely used as a fertilizer is?

  Options:
  A) galena
  B) bauxite
  C) emerald
  D) nitrochalk
  Show Answer
  The correct answer is D .
• Question 248: The colour of methyl orange in alkaline medium is Options:
  A) yellow
  B) pink
  C) orange
  D) red
  Show Answer
  The correct answer is A .
• Question 249: At 25^oC and 1atm, a gas occupies a volume of 1.50dm³. What volume will it occupy at 100^oC and 1atm? Options:
  A) 1.88 dm³
  B) 6.00 dm³
  C) 18.80 dm³
  D) 18.80 dm³
  E) 60.00dm³
  Show Answer
  The correct answer is A .
• Question 250: When H₂S is passed into a solution of iron (III) chloride, the solution turns Options:
  A) Pale green
  B) Pale red
  C) Brown
  D) Colourless
  Show Answer
  The correct answer is A .