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 641: Which of the reactions occurs at the anode during the electrolysis of a very dilute aqueous solution of sodium chloride? Options:
  A) OH^- - e → OH
  B) CIsup>- - e → CI
  C) OHsup>- + CIsup>-HCI + O₂
  D) Na₊ - esup>- Hg (Na)/(Hg) amalgam
  Show Answer
  The correct answer is A .
• Question 642: The synthetic detergents are preferred to soap for laundry using hard water because? Options:
  A) detergents are water soluble while soap is not
  B) the calcium salts of detergents are water soluble
  C) the magnesium salt of soap is soluble in hard water
  D) soap does not have a hydrocarbon terminal chain
  Show Answer
  The correct answer is B .
• Question 643: The product obtained when a mixture of benzene vapour and hydrogen are passed over nickel catalyst at 180^oC is Options:
  A) cyclohexane
  B) cyclopentane
  C) n- hexane
  D) n - pentane
  Show Answer
  The correct answer is A .
• Question 644: The atomic number of an element whose cation, X²⁺, has the ground state electronic configuration 1s²2s²2p⁶3s²2p⁶ is? Options:
  A) 16
  B) 18
  C) 20
  D) 22
  E) 24
  Show Answer
  The correct answer is C .
• Question 645: Detergents are more advantageous than soaps in hard water districts because Options:
  A) on treatment with hard water they either form soluble calcium salts or do not react with calcium ion
  B) on treatment with hard water they form soluble calcium salts
  C) on treatment with hard water they form sodium salts
  D) on treatment with hard water they are converted into soaps
  E) on treatment with hard water they form more lather than soaps does
  Show Answer
  The correct answer is A .
• Question 646:

  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 647:

  What volume of oxygen is produced from the decomposition of 2 mole of KCIO₃ at s.t.p?

  [Molar volume of a gas at s.t.p = 22.4 dm³]

  Options:
  A) 22.4 dm³
  B) 33.6 dm³
  C) 44.8 dm³
  D) 67.2 dm³
  Show Answer
  The correct answer is D .
• Question 648:

  

  The set-up above would be useful for determining the amount of

  Options:
  A) oxygen in air
  B) water vapour in air
  C) CO₂ in air
  D) arygen in air
  Show Answer
  The correct answer is B .
• Question 649: The stability of the noble gases is due to the fact that they Options:
  A) have no electron in their outermost shells
  B) have duplet or octet electron configurations
  C) belong to group zero of the periodic table
  D) are volatile in nature
  Show Answer
  The correct answer is B .
• Question 650:

  What is the state of matter in which particles are widely spaced and move freely with high kinetic energy?

  Options:
  A) Liquid
  B) Solid
  C) Plasma
  D) Gas
  Show Answer
  The correct answer is D .