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 251: Metals of the first transition series have special properties which are different from those of groups I and II elements because they have partially filled Options:
  A) s orbitals
  B) p orbitals
  C) d orbitals
  D) f orbitals
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  The correct answer is C .
• Question 252: The reaction between hydrogen and iodine may be represented by the equation H₂(g)+ I₂(g) → 2HI(g), and is exothermic. Therefore Options:
  A) an increase in temperature favours the forword reaction
  B) an increase in pressure favours the backward reaction
  C) both pressure and temperature muct be increased to favour the forward reaction
  D) a decrease in temperature will favour the forward reaction
  E) a decrease in pressure and an increase in temperature will favour the forward reaction
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  The correct answer is D .
• Question 253: A concentrated solution containing H⁺, Cu²⁺,OH^- and CI^- was electrolysed using platiunm electrodes which of the ions will be discharged at the cathods? Options:
  A) H⁺
  B) Cu²⁺
  C) OH^-
  D) CI^-
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  The correct answer is B .
• Question 254:

  Which transition metal is known for its multiple colorful oxidation states and compounds used in pigments and paints?

  Options:
  A) Silver (Ag)
  B) Copper (Cu)
  C) Gold (Au)
  D) Zinc (Zn)
  Show Answer
  The correct answer is B .
• Question 255: The gas that gives brown colouration in brown ring test is Options:
  A) NO
  B) CO₂
  C) NO₂
  D) CO
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  The correct answer is A .
• Question 256:

  The refreshing and characteristic taste of soda water and other soft drinks is as a result of the presence of

  Options:
  A) carbon(IV)oxide
  B) carbon(ll)oxide
  C) soda
  D) glucose
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  The correct answer is A .
• Question 257:

  Which of the following could not be alkane?

  Options:
  A) C${}_4$H${}_{10}$
  B) C${}_5$H${}_{12}$
  C) C${}_7$H${}_{14}$
  D) C${}_8$H${}_{18}$
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  The correct answer is C .
• Question 258: On recrystallization, 20g of magnesium tetraoxosuphate (IV) forms 41 g of magnesium tetraoxosulphate (IV) crystals, MgSO₄. yH₂O. The value of y is?(Mg = 24, S = 32, O = 16, H = 1) Options:
  A) 1
  B) 3
  C) 5
  D) 7
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  The correct answer is D .
• Question 259:

  200cm${}^3$ of 0.50mol/dm${}^3$ solution of calcium hydrogen trioxocarbonate (IV) is heated. The maximum weight of solid precipitated is

  Options:
  A) 10g
  B) 25g
  C) 20g
  D) 15g
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  The correct answer is A .
• Question 260:

  An organic compound contains 69% carbon, 15.3% hydrogen and 30.7% oxygen. Calculate the the empirical formula [C=12, H = 1, O = 16]

  Options:
  A) C${}_4$H${}_{1}2$O
  B) C${}_3$H${}_9$O
  C) C${}_4$H${}_9$O
  D) C${}_3$H${}_8$O
  Show Answer
  The correct answer is D .