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 721: A rock sample was added to cold dilute HNO₃. The gas evolved was passed into a solution of acidified K₂Cr₂O₇ and the solution turned green. The sample contains Options:
  A) Cl^-
  B) NO₃^-
  C) SO₃^2-
  D) SO₄^2-
  Show Answer
  The correct answer is C .
• Question 722: Carbohydrates are large molecules with the molecular formula C _x (H₂O)_y. In which of the following pairs is x not equal to y? Options:
  A) glucose and starch
  B) maltose and starch
  C) sucrose and fructose
  D) maltose and starch
  Show Answer
  The correct answer is A .
• Question 723: A basic postulate of the kinetic theory of gases is that the molecules of a gas move in straight lines between collisions. This implies that? Options:
  A) collisions are perfectly elastic
  B) forces of repulsion exist
  C) forces of repulsion are in equilibrium
  D) collision are inelastic
  Show Answer
  The correct answer is A .
• Question 724: How many moles of (H+) are there in 1 dm³ of 0.5 M solution of H₂SO₄? Options:
  A) 2.0 moles
  B) 1.0 moles
  C) 0.5 mole
  D) 0.25 mole
  Show Answer
  The correct answer is B .
• Question 725: A substance that is used as a ripening agent for fruits is Options:
  A) ethene
  B) propene
  C) methane
  D) butane
  Show Answer
  The correct answer is A .
• Question 726: Ammonium chloride can be separated from its mixture with common salt by Options:
  A) Distillation
  B) Evaporation
  C) Decantation
  D) Sublimation
  Show Answer
  The correct answer is D .
• Question 727: the elements that belong to the third period of the periodic table are Options:
  A) Li, Be, Al and P
  B) Na, P, O and Cl
  C) B, C, N and O
  D) Nz, Mg, S and Ar
  Show Answer
  The correct answer is D .
• Question 728: Which of the following is a physical change? Options:
  A) Freezing ice cream
  B) dissolving calcium in water
  C) burning kerosene
  D) Exposing white phosphorus to air
  Show Answer
  The correct answer is A .
• Question 729:

  Elements in the periodic table are arranged in the order of their

  Options:
  A) atomic numbers
  B) metallic character
  C) mass number
  D) relative atomic mass
  Show Answer
  The correct answer is A .
• Question 730: An element X has electron configuration 1s² 2s² 2p⁶ 3s² 3p⁵. Which of the following statements is correct about the element? Options:
  A) lt has a completely filled p-orbital
  B) lt has 5 electrons in its outermost shell.
  C) lt belongs to group ll on the periodic table
  D) lt is a halogen
  Show Answer
  The correct answer is D .