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 1041:

  

  In the solubility curve above, water at 98^oC is saturated with KCL and KCIO₃ What is the percentage of KCL impurity in the crystals formed when the solution is cooled to 30 ^oC?

  Options:
  A) 51.5
  B) 45.5
  C) 34.5
  D) 26.5
  Show Answer
  The correct answer is C .
• Question 1042:

  What is the mass (in grams) of 500 mL of ethanol? (density of ethanol = 0.789 g/mL)

  Options:
  A) 394.5 mL
  B) 500 mL
  C) 394.5 g
  D) 500 g
  Show Answer
  The correct answer is C .
• Question 1043: In the extraction of iron in the blast furnace, limestone is used to? Options:
  A) release CO₂ for the reaction
  B) reduce the iron ore
  C) increase the strenght of the iron
  D) remove impurities
  Show Answer
  The correct answer is D .
• Question 1044: Which of the following molecules has two other positional isomers? Options:
  A) CH₃CH₂Br
  B) CH₃CHBrCH₃
  C) CBr₂F₂
  D) CH₂CHBrCH₂Br
  Show Answer
  The correct answer is D .
• Question 1045: For iron to rust, there should be present? Options:
  A) oxygen
  B) moisture
  C) carbondioxide
  D) oxygen and moisture
  E) oxygen, moisture and carbondioxide
  Show Answer
  The correct answer is D .
• Question 1046: The pH of four solutions W, X, Y, Z are 4, 6, 8, 10 respectively, therefore Options:
  A) none of these solutions is acidic
  B) the pH of Y is made more acidic by addition of distilled water
  C) Z is the most acidic solution
  D) W is the most acidic solution
  E) X is neutral
  Show Answer
  The correct answer is D .
• Question 1047: The main impurity in iron ore during the extraction of iron is Options:
  A) Silicon (IV) oxide
  B) Carbon (IV) oxide
  C) Calcium trioxosilicate
  D) Sulphur (II) oxide
  Show Answer
  The correct answer is A .
• Question 1048: An example of element that can catenate is Options:
  A) bromine
  B) nitrogen
  C) chlorine
  D) carbon
  Show Answer
  The correct answer is D .
• Question 1049: Which of the following compounds is the best possible anti-knock agent for petrol? Options:
  A) (CH₃)₂CH - CH(CH₃)CH₂CH₃
  B) CH₃CH₂(CH₃)CHCH₂CH₂CH₃
  C) CH₃CH₂(CH₃)CHCH₂CH₂CH₃
  D) (CH₃)₃C - CH₂CH₂CH₃
  Show Answer
  The correct answer is A .
• Question 1050:

  117.0g of sodium chloride was dissolved in the solubility in 1.0dm³ of distilled water at 25^oC. Determine the solubility in mol dm^-3 of sodium chloride at that temperature

  [Na = 23, Cl = 35.5]

  Options:
  A) 1.0
  B) 2.0
  C) 3.0
  D) 4.0
  Show Answer
  The correct answer is B .