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:

  

  The above diagram gives the potential energy profile of the catalyst and uncatalysed reactions of X_(g) + Y_(g) → XY_(g). Deduce the respective activation energies in KJ of the catalysed and uncatalysed reverse reactions: XY(g) → X_(g) + Y_(g)

  Options:
  A) 300, 500
  B) 500, 300
  C) -300, -500
  D) -500, -300
  Show Answer
  The correct answer is A .
• Question 242: How many unpaired electron(s) are there in the nitrogen sub-levels/ Options:
  A) 3
  B) 2
  C) 1
  D) none
  Show Answer
  The correct answer is A .
• Question 243:

  

  Use the graph above to answer this question. The structure of cis-2-butene is

  Options:
  A) A
  B) B
  C) C
  D) D
  Show Answer
  The correct answer is B .
• Question 244: A difference between chemical and physical change is that in a chemical change Options:
  A) oxygen is consumed
  B) heat is supplied
  C) the reversible process occurs
  D) a new substance is formed
  Show Answer
  The correct answer is D .
• Question 245: In countries where the temperature fall below 273k, salt always spilled on the ray road in order to Options:
  A) increase the making point office
  B) increase the density of the ice
  C) make the ice impure
  D) rinse the making point of the ice
  Show Answer
  The correct answer is A .
• Question 246:

  MnO_4(aq) + 8H + 5Fe²⁺ $\to$ Mn²⁺_(aq) + 5Fe³⁺_(aq) + H₂O.

  The oxidation number of manganese in the above reaction changed from

  Options:
  A) +7 to +2
  B) +6 to +2
  C) +5 to +2
  D) +4 to +2
  Show Answer
  The correct answer is A .
• Question 247:

  The alkanoic acid found in human sweat is

  Options:
  A) CH${}_3$-COOH
  B) CH${}_3$—CH${}_2$—COOH
  C) H-COOH
  D) CH${}_3$
  Show Answer
  The correct answer is B .
• Question 248:

  Which of the following factors does NOT affect the rate of a chemical reaction?

  Options:
  A) Concentration of reactants
  B) Presence of a catalyst
  C) Molecular weight of products
  D) Temperature
  Show Answer
  The correct answer is C .
• Question 249: The relative atomic mass of a naturally occurring lithium consisting of 90%$\frac{7}{3}$Li and 10%$\frac{6}{3}$Li is Options:
  A) 6.2
  B) 6.8
  C) 7.1
  D) 6.9
  Show Answer
  The correct answer is D .
• Question 250: A gas that will turn orange potassium heptaoxodichromate (lV) solution to clear green is? Options:
  A) sulphur (ii) oxide
  B) hydrogen sulphide
  C) sulphide (lV) oxide
  D) hydrogen chloride
  Show Answer
  The correct answer is A .