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 2021: Sodium hydrogen should be stored in properly closed containers because it? Options:
  A) readily asborbs water vapour to air
  B) is easily oxidize by atmospheric oxygen
  C) turns golden yellow when exposed to light
  D) melts at a low temperature
  Show Answer
  The correct answer is A .
• Question 2022: The energy change (ΔH) for the reaction CO(g) + (1)/(2)O_2(g) → is?(ΔHi(CO) = -110.4 kJ mol^-) (ΔHi(CO₂) = -393 kJ mol^-) Options:
  A) -503.7 kJ
  B) +503.7kJ
  C) -282.9 kJ
  D) +282.9 kJ
  E) +393.3 kJ
  Show Answer
  The correct answer is C .
• Question 2023: A sample of an oxide of mercury weighed 1.00g. When this was heated, oxygen was given off, and 1.00g of mercury metal only was left. What is the formula of the oxide? Options:
  A) Hg₂O
  B) HgO₂
  C) HgO₂
  D) HgO
  E) None of the above
  Show Answer
  The correct answer is E .
• Question 2024:

  The sub-atomic particles located in the nucleus of an atomare?

  Options:
  A) neutron and proton
  B) proton and electron
  C) proton and ions
  D) neutron and electron
  Show Answer
  The correct answer is A .
• Question 2025: Which of the following statements is NOT true of electrovalent compounds? Options:
  A) They are solids
  B) They do not vaporized easily
  C) They usually dissolve in water
  D) The elements forming the compounds normally have their valency electrons in a shared state
  E) They conduct electricity
  Show Answer
  The correct answer is D .
• Question 2026: How will a metal X, which reacts explosively with air and with dilute acids be best extracted from its ores? Options:
  A) Electrolysis of solution of its salts
  B) Decomposition of its oxides
  C) Displacement from solution by an alkali metal
  D) Electroiysis of fused salt
  Show Answer
  The correct answer is D .
• Question 2027: In countries where the temperature falls below 273K, salt is always sprinkled on the icy road in order to Options:
  A) lower the melting point of the ice
  B) increase the density of the ice
  C) make the ice impure
  D) raise the melting point of the ice
  Show Answer
  The correct answer is A .
• Question 2028: 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 .
• Question 2029: A chemical reaction which the hydration energy is greater than the lattice energy is referred to as Options:
  A) a spontaneous reaction
  B) an endothermic reaction
  C) an exothermic reaction
  D) a reversible reaction
  Show Answer
  The correct answer is C .
• Question 2030: A substance S is isomorphous with another substance R. When a tiny crystals of S is added into a supersaturated solution of R? Options:
  A) S dissolves in the solution
  B) crystals of R are precipitated
  C) there is no observable change
  D) R and S react to generate heat
  Show Answer
  The correct answer is B .