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 901: The reaction of an alkene with hydrogen in the presence of catalyst is Options:
  A) a substitution reaction
  B) an oxidation reaction
  C) a nucleophilic reaction
  D) an addition reaction
  Show Answer
  The correct answer is D .
• Question 902: When water boilers are used for long period of time, the solid substances left behind as scale are Options:
  A) magnesium trioxosilicate (IV) and rust
  B) magnesium trioxosilicate (IV) and calcium tetraoxosulphate (VI)
  C) clay and magnesium troxosulphate (IV)
  D) clay and rust
  Show Answer
  The correct answer is A .
• Question 903:

  NH_3(g) + HCl_(g) → NH₄Cl_(s)

  The entropy change in the system above is

  Options:
  A) negative
  B) indeterminate
  C) positive
  D) zero
  Show Answer
  The correct answer is A .
• Question 904:

  What is the maximum number of electrons that can occupy the second energy level (n=2)?

  Options:
  A) 2 electrons
  B) 18 electrons
  C) 8 electrons
  D) 32 electrons
  Show Answer
  The correct answer is C .
• Question 905:

  Na₂CO₃ + 2HCI → 2NaCI + H₂O + CO₂. Using the above equation, what volume of carbondioxide, measured at s.t.p is liberated when 53g of sodium carbonate is dissolved in hydrochloric acid?

  (1 mole of gas occupies 22.4 dm³ at s.t.p)

  (Na = 23, C = 12, O = 16)

  Options:
  A) 44.8 dm³
  B) 11.2 dm³
  C) 100.1 dm³
  D) 3.0 dm³
  E) 22.4 dm³
  Show Answer
  The correct answer is B .
• Question 906:

  A given volume of methane diffuses in 20s. How long will it take the same volume of sulphur (IV) oxide to diffuse under the same conditions?

  [C = 12, H = 1, S = 32, O = 16].

  Options:
  A) 5s
  B) 20s
  C) 40s
  D) 60s
  Show Answer
  The correct answer is C .
• Question 907:

  Two equal bulbs, one containing ammonia and the other nitrogen are opened mouth-to-mouth to each other at room temperature. The entropy in the mixture of gases is likely to

  Options:
  A) remain unchanged
  B) increase
  C) decrease
  D) change
  Show Answer
  The correct answer is B .
• Question 908: When few drops of concentrated trioxonitrate(V) acid is added to an unknown sample and wanned an intense yellow colouration is observed. The likely functional group present in the sample is Options:
  A) NH₃—C—C=O
  B) CHO
  C) CO
  D) CNH₂
  Show Answer
  The correct answer is A .
• Question 909: What volume of 11.0 M hydrochloric acid must be dilute to obtain 1 dm³ of 0.05 M acid? Options:
  A) 0.05 dm³
  B) 0.10 dm³
  C) 0.55 dm³
  D) 11.0 dm³
  Show Answer
  The correct answer is A .
• Question 910: The reaction that takes place in Daniell cell is Options:
  A) direct combination
  B) redox
  C) double decomposition
  D) neutralization
  Show Answer
  The correct answer is B .