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 1021: 20 cm ³ of hydrogen gas are sparked with 20cm ³ of oxygen gas in an endimoeter at 373k (100 ^oC) and 1 atmosphere. The resulting mixture is cooled to 298 K (25 ^oC) and passed over calcium chloride. The volume of the residual gas is Options:
  A) 40 cm ³
  B) 20 cm ³
  C) 30 cm ³
  D) 10cm ³
  E) 5cm ³
  Show Answer
  The correct answer is D .
• Question 1022: How many valence electrons are contained in the element represented ³¹₁₅P? Options:
  A) 3
  B) 5
  C) 15
  D) 31
  Show Answer
  The correct answer is B .
• Question 1023: Which of the following compounds gives a yellow residue when heated and also reacts with aqueous sodium hydroxide to give a white gelatinous precipitate soluble in excess sodium hydroxide solution? Options:
  A) (NH₄)CO₃
  B) ZnCO₃
  C) Al₂(SO₄)₃
  D) PbCO3
  Show Answer
  The correct answer is B .
• Question 1024: In the production of soap, concentrated sodium chloride solution is added to Options:
  A) increase the solubility of soap
  B) decrease the solubility of the soap
  C) saponify the soap
  D) emulsify the soap
  Show Answer
  The correct answer is B .
• Question 1025: A fixed mass of gas has a volume of 92cm₃ at 3 ^oC. When will be its volume at 18 ^oC if the pressure remains constant Options:
  A) 15.3cm³
  B) 87.3cm³
  C) 552.0cm³
  D) 97.0cm³
  Show Answer
  The correct answer is D .
• Question 1026:

  

  Which of the five atoms can be described by the following properties: Relative atomic mass is greater than 30 but less than 40, it has odd atomic number and forms a unipositive ion in solution?

  Options:
  A) T
  B) W
  C) X
  D) Y
  E) Z
  Show Answer
  The correct answer is D .
• Question 1027:

  

  The IUPAC nomenclature for the structure above is

  Options:
  A) 2, 3 - dichloro - 4, 4, 5 - trimethyl pent - 2 - ene
  B) 4, 5 - dichloro - 2, 3 - dimethyl hex - 2 - ene
  C) 2, 3 - dichloro - 4, 4 - dimethyl hex - 2- ene
  D) 2, 3 dichloro - 2, 2 - dimethyl hex - 2 - ene
  Show Answer
  The correct answer is C .
• Question 1028: Nigerian crude oil is described as light crude because of its Options:
  A) low sulphur content
  B) high natural gas content
  C) high octane number
  D) low aliphatic-hydrocarbon content
  Show Answer
  The correct answer is A .
• Question 1029: CO_g + H₂O_g $\to$ _2g + H_2g $\mathrm{\Delta }$H = -4100J. Which of the following factors favour the formation of hydrogen in the above reaction? i. high pressure. ii. low pressure iii. high temperature iv. use of excess steam Options:
  A) i, iii and iv
  B) iii only
  C) ii, iii and i
  D) iv only
  Show Answer
  The correct answer is D .
• Question 1030: The pollutant that contributes to the depletion of the ozone layer is Options:
  A) CFCs
  B) NO₂
  C) SO₂
  D) CO
  Show Answer
  The correct answer is A .