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 221:

  Na₂S₂O_3(aq) + 2HCl_(aq) → 2NaCl_(aq) + H₂O_(l)

  Which of the following would introduce the greatest increase in the rate of the chemical reaction above?

  Options:
  A) An increase in temperature and decrease in the concentration of the reactant
  B) A decrease in the volume and increase in the pressure of the reactant
  C) A decrease in the temperature and an incease in the concentration of the reactant
  D) An increase in temperature and an increase in the concentration of the reactant
  Show Answer
  The correct answer is D .
• Question 222: What are the possible oxidation numbers of an element if its atomic number is 17? Options:
  A) -1 and 7
  B) -1 and 6
  C) -3 and 5
  D) -2 and 6
  Show Answer
  The correct answer is A .
• Question 223: Which of the following is the correct order of decreasing activity of the metals Fe, Ca, Al and Na? Options:
  A) Fe> Ca> Al> Na
  B) Na> Ca> Al> Fe
  C) Al> Fe> Na> Ca
  D) Ca> Na> Fe>, Al
  Show Answer
  The correct answer is B .
• Question 224:

  How many grams of H₂SO₄ are necessary for the preparation of 0.175 dm³ of M 6.00 M H₂SO₄?

  (S = 32.06, O = 16.00 H = 1.00)

  Options:
  A) 206.0 g
  B) 103.0 g
  C) 98.1 g
  D) 51.5 g
  Show Answer
  The correct answer is B .
• Question 225: A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen. If the molar mass of the compound is 180, Find the molecular formula [H = 1, C = 12, O = 16) Options:
  A) CH₂O
  B) C₃H₆O₃
  C) C₆H₁₂O₆
  D) C₆H₁₂O₃
  Show Answer
  The correct answer is C .
• Question 226: Five compounds R,T,W,X and Y form the following compounds: a basic hydride R.H, an acidic hydride YH, atmospheric oxide W₂O₃, XO₂. which of the elements is an alkali Options:
  A) R
  B) T
  C) W
  D) X
  E) Y
  Show Answer
  The correct answer is A .
• Question 227: Oil spillage in ponds and creeks can be cleaned up by? Options:
  A) burning off the oil layer
  B) spraying with detergent
  C) dispersal with compressed air
  D) spraying with hot water
  Show Answer
  The correct answer is B .
• Question 228: Which of the following physical properties decreases down a group in the periodic table? Options:
  A) Atomic radius
  B) Ionic radius
  C) Electropositivity
  D) Electronegativity
  Show Answer
  The correct answer is B .
• Question 229: Which of the following class of compounds can exist as dipolar ions in solution? Options:
  A) Alkanoic acid
  B) Fatty acids
  C) Dialkanoic acids
  D) Amino acids
  Show Answer
  The correct answer is D .
• Question 230: Given that electronegativity increases across a period and decreases down a group in the periodic table, in which of the following compounds will the molecules be held together by the strongest hydrogen bond? Options:
  A) HF_(g)
  B) NH_3(g)
  C) CH_4(g)
  D) HCl_(g)
  Show Answer
  The correct answer is A .