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 271: The equilibrium of an endothermic reaction which proceeds with an increase in volume can be shifted in the reverse direction by Options:
  A) increasing the temperature and decreasing the pressure
  B) increasing the pressure and increasing the temperature
  C) decreasing the temperature and increasing the pressure
  D) decreasing the pressure and decreasing the temperature
  Show Answer
  The correct answer is C .
• Question 272: A mixture of starch solution and potassium iodide was placed in a test tube. On adding dilute tetraoxosulphate (lV) acid and then K₂Cr₂O₇ solutions, a blue-black colour was produced. In this reaction, the? Options:
  A) iodide is oxidized
  B) tetraoxosulphate (Vl) acid acts as an oxidizing agent
  C) starch has been oxidized
  D) K₂Cr₂O₇ is oxidized
  Show Answer
  The correct answer is C .
• Question 273: In the reaction of oxygen with hydrogen to produce water, which of the following statements is true? Options:
  A) One atom of hydrogen reacts with two atoms of oxygen to give one molecule of water
  B) Two atoms of hydrogen react with two atoms of oxygen to give two molecules of water
  C) One molecule of oxygen reacts with one molecule of hydrogen to give two molecules of water
  D) One molecule of hydrogen reaccts with two molecules of oxygen to give three molecules of water
  E) One molecule of oxygen reacts with two molecules of hydrogen to give two molecules of water
  Show Answer
  The correct answer is E .
• Question 274:

  An organic compound X has the following properties:
  I. It is not miscible with water.
  ll. It has boiling point of 77^oC.
  lll. It has a sweet odour.
  IV. lt is insoluble in sodium hydrogen carbonate solution.
  V lt does not decolourize bromine water.
  X is therefore

  Options:
  A) methane
  B) ethanoic acid
  C) ethene
  D) ethyl ethanoate
  E) carbon tetrachloride
  Show Answer
  The correct answer is D .
• Question 275: A major factor considered in selecting a suitable method for preparing a simple salt is its Options:
  A) Crystalline from
  B) melting point
  C) reactivity with dilute acids
  D) solubility in water
  Show Answer
  The correct answer is D .
• Question 276:

  

  In the diagram above, the gas produced is

  Options:
  A) NO
  B) NO₂
  C) N₂O
  D) N₂O₄
  Show Answer
  The correct answer is A .
• Question 277: What mass of sodium carbonate solution is in 500 cm³ of 0.1 molar sodium carbonate solution?(Na = 23, C = 12, O = 16) Options:
  A) 10.6 g
  B) 5.3 g
  C) 500 g
  D) 10 g
  E) 20 g
  Show Answer
  The correct answer is B .
• Question 278: Which of the following pairs of substance will react further with oxygen to form a higher oxide? Options:
  A) CO₂ and H₂O
  B) NO and H₂O
  C) CO and CO₂
  D) SO₂ and NO
  Show Answer
  The correct answer is D .
• Question 279: Alloys are best prepared by Options:
  A) Electroplating
  B) Arc-welding
  C) Reducing and mixture of their metallic oxide
  D) Cooling a molten mixture of the metals
  Show Answer
  The correct answer is D .
• Question 280:

  The process of rusting is an example of the formation of

  Options:
  A) Basic oxide
  B) Acidic oxide
  C) Reducing oxide
  D) Amphoteric oxide
  Show Answer
  The correct answer is A .