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 681:

  2H_2(g) + O_2(g) → 2H₂ O_(g)

  In the reaction above, what volume of hydrogen would be left over when 300 cm³ of oxygen and 1000 cm³ of hydrogen are exploded in a sealed tube?

  Options:
  A) 200 cm³
  B) 400 cm³
  C) 600 cm³
  D) 700 cm³
  Show Answer
  The correct answer is B .
• Question 682: Element X has a total of 19 electrons and can react with oxygen to form an oxide. Which of the following statements is NOT true of the oxide of the element? Options:
  A) When exposed to air, it slowy changes to liquid
  B) its solution in water conducts electricity
  C) Its solution in water, on evaporationm gives a white solid
  D) Its solution in water liberates hydroge when in contact with aluminium metal
  E) Its oxide, when stronlgy heated, regenerates the elements X
  Show Answer
  The correct answer is A .
• Question 683:

  1.1 g of CaCI₂ dissolved in 50 cm³ of water caused a rise in temperature of3.4°C. The heat of reaction, ∆H for CaCI₂ in kj per mole is?

  (Ca = 40, CI = 35.5, specific heat of water is 4.18 jk^-1

  Options:
  A) -71.1
  B) -4.18
  C) +71.1
  D) +111.0
  Show Answer
  The correct answer is A .
• Question 684: An increase in temperature causes an increase in the pressure of a gas because there is an increase in the? Options:
  A) average velocity of the molecules
  B) number of collisions between the molecules
  C) density of the molecules
  D) free mean path between each molecules and other
  Show Answer
  The correct answer is B .
• Question 685: 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 686: A mixture of iodine and sulphur crystals can be separated by treatment with Options:
  A) water to filter off sulphur
  B) carbon (IV) suiphide to filter off iodine
  C) ethanoic acid to filter off sulphur
  D) methanol to filter off iodine
  Show Answer
  The correct answer is B .
• Question 687: In the periodic table, what is the property that decreases along the periodic and increases down the group? Options:
  A) Atomic number
  B) Electron affinity
  C) Ionization potential
  D) Atomic radius
  Show Answer
  The correct answer is D .
• Question 688: When ammonia and hydrogen ion bond together to form ammonium ion, the bond formed is called Options:
  A) ionic bond
  B) electrovalent bond
  C) covalent bond
  D) co-ordinate bond
  E) hydrogen bond
  Show Answer
  The correct answer is D .
• Question 689: Which of the following molecules has two other positional isomers? Options:
  A) CH₃CH₂Br
  B) CH₃CHBrCH₃
  C) CBr₂F₂
  D) CH₂CHBrCH₂Br
  Show Answer
  The correct answer is D .
• Question 690: 2-methylprop-1-ene is an isomer of Options:
  A) but-2-ene
  B) pent-1-ene
  C) 2-methylbut-2-ene
  D) 2-methylbut-1-ene
  Show Answer
  The correct answer is A .