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 621:

  

  The diagram above represents the formation of

  Options:
  A) a metallic bond
  B) an electrovalent bond
  C) a covalent bond
  D) a coordinate covalent bond
  Show Answer
  The correct answer is C .
• Question 622: When a solution of silver (l) nitrate is saturated with hydrogen sulphide, a black precipitate forms which is? Options:
  A) H₂S
  B) Ag₂S
  C) PbS
  D) HNO₃
  E) S
  Show Answer
  The correct answer is B .
• Question 623:

  Consider the equation below:

  Cr${}_2$O${}_7^{2-}$ + 6Fe${}^{2+}$ + 14H${}^{+}$ $\to$ 2Cr${}^{3+}$ + 6Fe${}^{3+}$ + 7H${}_2$O.

  The oxidation number of chromium changes from

  Options:
  A) +5 to +3
  B) +6 to +3
  C) -2 to +3
  D) +7 to +3
  Show Answer
  The correct answer is B .
• Question 624: Which of the following will produce a solution with pH less than 7 at equivalent point? Options:
  A) HNO ₃ +NaOH
  B) H ₂SO ₄ + KOH
  C) HC +Mg (OH) ₂
  D) HNO ₃ + KOH
  Show Answer
  The correct answer is C .
• Question 625: Some products of destructive distillation of coal are Options:
  A) carbon (IV) oxide and ethanoic acid
  B) trioxocarbonate (IV) acid and methanoic acid
  C) producer gas and water gas
  D) coke and ammonia liquor
  Show Answer
  The correct answer is D .
• Question 626: In which of the following reactions does reduction takes place Options:
  A) Fe²⁺ - e^- → Fe³⁺
  B) 2O^2- →O₂ + 4e^-
  C) Cr – 2e^- → Cr²⁺
  D) 2H⁺ + 2e^- → H₂
  Show Answer
  The correct answer is D .
• Question 627:

  How many bonding pair are present in carbon(iv)oxide?

  Options:
  A) 4
  B) 3
  C) 2
  D) 1
  Show Answer
  The correct answer is A .
• Question 628: In the course of an experiment, two gases X and Y were produced. X turned wet lead ethanoate to black and Y bleached moist litmus paper. What are the element(s) in each of the gases X and Y respectively? Options:
  A) H and S;Cl
  B) H and O;Cl
  C) H and S;C and O
  D) H and Cl;S and O
  Show Answer
  The correct answer is A .
• Question 629:

  I. It has a varied composition from one place to another.

  II. It constituents can be separated by physical means.

  III. It contains unreactive noble gases

  Which of the above shows that air is a mixture?

  Options:
  A) I and II only
  B) II and III only
  C) I and III only
  D) I, II and III
  Show Answer
  The correct answer is A .
• Question 630: Cotton is almost pure? Options:
  A) starch
  B) protein
  C) animal fibre
  D) celluose
  E) mineral fibre
  Show Answer
  The correct answer is D .