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: How many coulombs of electricity are passed through a solution in which 6.5 amperes are allowed to run for 1.0 hour? Options:
  A) 3.90 x 10² coulombs
  B) 5.50 x 10³ coulombs
  C) 6.54 x 10³ coulombs
  D) 2.34 x 10⁴ coulombs
  Show Answer
  The correct answer is D .
• Question 242:

  

  The diagram above (Fig.3) shows the energy profile for the reaction A + B + = C + D From this diagram, it is clear that the reaction is

  Options:
  A) spontaneous
  B) isothermal
  C) adiabatic
  D) exothermic
  E) endothermic
  Show Answer
  The correct answer is D .
• Question 243:

  If the heat of combustion of hydrogen is -285.8kJ,

  What is the heat of formation of water?

  Options:
  A) +571.6 kJ
  B) -571.6 kJ
  C) -285.8 kJ
  D) +285.8 kJ
  Show Answer
  The correct answer is C .
• Question 244:

  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 245: Two hydrocarbons X and Y were treated with bromine water. X decolorised the solution and Y did not not. Which class of compound does Y belong? Options:
  A) Benzene
  B) Alkynes
  C) Alkenes
  D) Alkanes
  Show Answer
  The correct answer is D .
• Question 246:

  What current will deposit 3.25g of zinc in 2hrs?

  [Zn = 65, F = 96500 mol^-]

  Options:
  A) 3.25A
  B) 2.00A
  C) 1.34A
  D) 0.67A
  Show Answer
  The correct answer is C .
• Question 247:

  If gas A has a molar mass of 32 g/mol and gas B has a molar mass of 64 g/mol, what is the ratio of their diffusion rates?

  Options:
  A) 2:1
  B) 1:2
  C) 1:1
  D) 1:4
  Show Answer
  The correct answer is A .
• Question 248: The leachate of a certain plant ash is used in local soap making because it contains Options:
  A) sodium chloride and potassium hydroxide
  B) sodium hydroxide
  C) potassium hydroxide
  D) soluble carbonates and hydrogen carbonates
  Show Answer
  The correct answer is B .
• Question 249:

  

  From the diagram above the mass of crystals deposited when 1 dm ³ of a saturated solution of NaCl is cooled from 80^oC to 60^oC is

  [Na = 23, Cl = 35.5]

  Options:
  A) 117.00 g
  B) 58.50 g
  C) 11.70 g
  D) 5.85 g
  Show Answer
  The correct answer is A .
• Question 250: The pollution from petroleum spillage in rivers and lakes can best be dispersed by Options:
  A) Pouring detergents
  B) Passing of ships through the area
  C) Pouring organic solvents
  D) Evaporation
  Show Answer
  The correct answer is A .