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 271: Which of the following salts can be melted without decomposition? Options:
  A) Na₂CO₃
  B) CaCO₃
  C) MgCO₃
  D) ZnCO₃
  Show Answer
  The correct answer is A .
• Question 272: 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
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  The correct answer is E .
• Question 273: When copper (ii) sulphate solution is treated with excess ammonium hydroxide, a precipitate is first formed, and then this dissolves to give a deep blue solution. This deep blue solution is a Options:
  A) Cu(OH)₂
  B) CuSo₄.5H₂O
  C) (NH₄)₂SO₄
  D) Cu(NH₃)₄(OH)₂
  E) CuSO₄.(NH₄)₂SO₄.2H₂O
  Show Answer
  The correct answer is E .
• Question 274: Hydrogen is not liberated when trioxonitrate(v)acid reacts with zinc because Options:
  A) zinx is not rendered passive by acid
  B) hydrogen produced is oxidized to water
  C) oxides of nitrogen are produced
  D) all nitrates are soluble in water
  E) trioxonitrate(v)acid is a strong acid
  Show Answer
  The correct answer is E .
• Question 275: Which of the following is NOT a redox reaction? Options:
  A) 2HNO₂ + 2HI → 2H₂O + 2NO + I₂
  B) Zn + H₂SO₄ → ZnSO₄ + H₂
  C) Ca(HCO₃)₂ → CaCO₃ + H₂O + CO₂
  D) 4FeO + O₂ → 2Fe₂O₃
  E) 2Na + Cl₂ → 2NaCl
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  The correct answer is C .
• Question 276: Farmlands affected by crude-oil spillage can be decontaminated by Options:
  A) Adding acidic solution
  B) Using aerobic bacteria
  C) Pouring water on the affected water area
  D) Burning off the oil from the area
  Show Answer
  The correct answer is B .
• Question 277: Which of the following reactions does not take place in the smelting of iron in a blast furnace? Options:
  A) CaCO_3(s) CaO_(s) + CO_2(g)
  B) C_(s) + O_2(g) CO_2(g)
  C) 3FeCO_(s) + 2OCO_2(g) FeO_4(s)
  D) SiO_2(s) + CaO_(s) CaCO_3(s)
  E) CO_2(g) + C_(s) 2CO_(g)
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  The correct answer is C .
• Question 278: The brown coloration in nitric acid prepared in the laboratory can be removed by? Options:
  A) heating the acid
  B) bubbling air through the acid
  C) cooling the acid
  D) adding a decolorizing agent
  E) adding a base
  Show Answer
  The correct answer is B .
• Question 279:

  X is a substance which liberates CO${}_2$ on treatment with concentrated H${}_2$SO${}_4$. A warm solution of X can decolorize acidified KMnO${}_4$. X is

  Options:
  A) HCOOH
  B) NaHCO${}_3$
  C) FeCO${}_3$
  D) H${}_2$C${}_2$O${}_4$
  Show Answer
  The correct answer is D .
• Question 280:

  Which of the following conditions will most enhance the spontaneity of a reaction?

  Options:
  A) $\mathrm{\Delta }$H is negative and greater than T$\mathrm{\Delta }$S
  B) $\mathrm{\Delta }$H is negative and $\mathrm{\Delta }$S = 0
  C) $\mathrm{\Delta }$H is positive and less than T$\mathrm{\Delta }$S
  D) $\mathrm{\Delta }$H is positive and equal to T$\mathrm{\Delta }$S
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  The correct answer is A .