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 531:

  In the reactions

  (I) H₂ (g) + 1/2O₂(g) → H₂O(l); ∆H = -286 KJ

  (II) C(s) + O₂g) → CO₂ (g); ∆H = -406 KJ the equations imply that

  Options:
  A) more heat is absorbed in (l)
  B) more heat is absorbed in (ll)
  C) less heat is evolved in (l)
  D) reaction (ll) proceeds faster than (l)
  E) reaction (l) proceeds faster than (ll)
  Show Answer
  The correct answer is C .
• Question 532:

  The contact process is used for the industrial production of

  Options:
  A) sulfuric acid (H2SO4)
  B) Hydrochloric acid (HCl)
  C) Sodium hydroxide (NaOH)
  D) Calcium oxide (CaO)
  Show Answer
  The correct answer is A .
• Question 533: To obtain pure carbon (II) oxide from its mixture with carbon (IV) oxide, the mixture should be Options:
  A) passed over heated copper (II) oxide
  B) bubbled through water
  C) bubbled through concentrated tetroxosulphate (VI) acid
  D) bubbled through sodium hydroxide
  Show Answer
  The correct answer is D .
• Question 534:

  In the preparation of salts, the method employed will depend on the?

  Options:
  A) composition
  B) dissociating ability
  C) stability to heat
  D) precipitating ability
  Show Answer
  The correct answer is C .
• Question 535: Which one of these compounds will NOT give an oxygen gas on heating? Options:
  A) Manganese dioxide
  B) Hydrogen peroxide
  C) Zinc nitrate
  D) Sodium nitrate
  E) Ammonium nitrate
  Show Answer
  The correct answer is E .
• Question 536: If 30cm³ of oxygen diffuses through porous plug in 7s, how long will it take 60 cm³ of chlorine to diffuse through the same plug? Options:
  A) 12s
  B) 14s
  C) 21s
  D) 30s
  Show Answer
  The correct answer is C .
• Question 537: A few drops of NaOH solution was added to an unknown salt forming a white precipitate which is insoluble in excess solution. The cation likely present is Options:
  A) Zn²⁺
  B) Pb²⁺
  C) Ca²⁺
  D) Al³⁺
  Show Answer
  The correct answer is C .
• Question 538:

  Chlorine, consisting of two isotopes of mass numbers 35 and 37, has an atomic mass of 35.5.

  The relative abundance of the isotope of mass number 37 is?

  Options:
  A) 20
  B) 25
  C) 50
  D) 75
  Show Answer
  The correct answer is B .
• Question 539:

  Burning magnesium ribbon in air removes which of the following

  (i) oxygen (ii) nitrogen (iii) argon and (iv) carbon(iv)oxide?

  Options:
  A) i and iv only
  B) i, ii, iii and iv only
  C) i only
  D) i and ii only
  Show Answer
  The correct answer is C .
• Question 540:

  An unknown organic compound X has a relative molecular mass of 180. It is a colourless crystaline solid, readily soluble in water. X contains the elements C, H and O in the atomic ratio 1: 2:1. The compound has a sweet teste and melts on heating. In the presence of yeast and in the absence of air, X is converted to compound Y and a colourless gas. Compound Y reacts with sodium metal to produce a gas Z which gives a 'pop' sound with a glowing splint. Y also reacts with ethanoic acid to give a sweet smelling compound W.

  Compound W is

  Options:
  A) a soap
  B) an oil
  C) an alkane
  D) an ester
  E) sucrose
  Show Answer
  The correct answer is D .