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 391: If the change in free energy of a system is -899 Jmol^-1 and the entropy change is 10Jmol^-1k^-1 at 250C, calculate the enthalpy change. Options:
  A) +2081 Jmol^-1
  B) -2081 Jmol^-1
  C) -649 Jmol^-1
  D) +649 Jmol^-1
  Show Answer
  The correct answer is A .
• Question 392: Magnesium ribbon was added to each of the following aqueous solution in turn: H₂SO₄, AgNO₃, HNO₃, HCl, NH₃, HCl, NH₃. In which case does the magnesium become covered with a dark precipitate? Options:
  A) H₂SO₄
  B) AgNO₃
  C) HNO₃
  D) NH₃
  E) HCl
  Show Answer
  The correct answer is B .
• Question 393:

  The collision theory explains reaction rates in terms of

  Options:
  A) size of the product
  B) frequency of collision of the reactants
  C) size of reactant
  D) frequency of collision of the products
  Show Answer
  The correct answer is B .
• Question 394:

  

  Use the option above to answer this question. The graph that describes a zero order reaction is

  Options:
  A) A
  B) B
  C) C
  D) D
  Show Answer
  The correct answer is B .
• Question 395:

  If a reaction is exothermic and there is a great disorder, it means that

  Options:
  A) The reaction is in a state of equilibrium.
  B) There will be a large increase in free energy.
  C) There will be a large decrease in free energy.
  D) The reaction is static.
  Show Answer
  The correct answer is C .
• Question 396: Which of the following will shift to the left from dilute tetraoxosulphate (VI) acid? Options:
  A) Lead
  B) Magnesium
  C) Cpper
  D) Gold
  Show Answer
  The correct answer is B .
• Question 397: The ability of carbon to form long chains is referred to as Options:
  A) Alkylation
  B) Acylation
  C) Carbonation
  D) Catenation
  Show Answer
  The correct answer is D .
• Question 398:

  What number of moles of Cu ²⁺ will be deposited by 360 coulombs of electricity?

  [f = 96500 C mol ^-1]

  Options:
  A) 5.36 x 10 ^-4 mole
  B) 1. 87 x 10 10 ^-3 mole
  C) 9. 35 x 10 ^-4 mole
  D) 3. 73 x 10 ^-3
  Show Answer
  The correct answer is B .
• Question 399: The oxidation of ammonia in excess air produces Options:
  A) NO
  B) N₂O
  C) NO₂
  D) N₂O₄
  Show Answer
  The correct answer is A .
• Question 400: Which of the following gases can be collected by the upward displacement of air? Options:
  A) NO
  B) H ₂
  C) NH₃
  D) Cl ₂
  Show Answer
  The correct answer is D .