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 1811:

  An unknown organic compound X has a relative molecular mass of 180. It is a colourless crystaline solid, readily soluble in water. X contains the elements C, H and O in the atomic ratio 1: 2:1. The compound has a sweet teste and melts on heating. In the presence of yeast and in the absence of air, X is converted to compound Y and a colourless gas. Compound Y reacts with sodium metal to produce a gas Z which gives a 'pop' sound with a glowing splint. Y also reacts with ethanoic acid to give a sweet smelling compound W.

  Compound W is

  Options:
  A) a soap
  B) an oil
  C) an alkane
  D) an ester
  E) sucrose
  Show Answer
  The correct answer is D .
• Question 1812: The removal of rust from iron by treatment with tetraoxosulphate (IV) acid is based on the? Options:
  A) hydrolysis of the iron
  B) reaction of acid with base
  C) oxidationof the rust
  D) dehydration of the iron
  Show Answer
  The correct answer is D .
• Question 1813: The products of the thermal decomposition of ammonium trioxonitrate (V) are Options:
  A) NO ₂ and oxygen
  B) NH₃ and oxygen
  C) nitrogen and water
  D) N₂O and water
  Show Answer
  The correct answer is D .
• Question 1814:

  Aluminum hydroxide is used in the dyeing industry as a?

  Options:
  A) Dye
  B) Dispersant
  C) Salt
  D) Mordant
  Show Answer
  The correct answer is D .
• Question 1815: Sodium carbonate crystals on exposure to a dry atmosphere change to a white powder. This phenomenon is known as? Options:
  A) deliquescence
  B) hygroscopy
  C) oxidation
  D) efforescence
  E) sublimation
  Show Answer
  The correct answer is D .
• Question 1816: Organic molecules that have the suffix-ene are unsaturated hydrocarbons that have Options:
  A) a single bond
  B) a double bond
  C) a triple bond
  D) an ionic bond
  Show Answer
  The correct answer is B .
• Question 1817: Which of these properties gives a solid its definite shape? Options:
  A) strong intermolecular attraction
  B) high melting point
  C) high boiling point
  D) weak intermolecular attraction
  Show Answer
  The correct answer is A .
• Question 1818: Oxygen is a mixture of two isotopes O and O with relative abundances of 90% and 10% respectively. The relative atomic mass of oxygen is? Options:
  A) 16.0
  B) 16.2
  C) 17.0
  D) 18.0
  Show Answer
  The correct answer is B .
• Question 1819:

  When anhydrous cobalt chloride paper is exposed to water, what color change is observed?

  Options:
  A) From pink to blue
  B) From white to blue
  C) From blue to white
  D) From blue to pink
  Show Answer
  The correct answer is D .
• Question 1820:

  GAS	CO${}_2$	N${}_2$	O${}_2$
  % BY VOLUME	4	72	24

  The above table shows the compositions of the atmosphere of planet X. Which of these gases are present inhigherpercentages on earth?

  Options:
  A) CO${}_2$ and O${}_2$
  B) N${}_2$ and CO${}_2$
  C) CO${}_2$, O${}_2$ and N${}_2$
  D) O${}_2$ and N${}_2$
  Show Answer
  The correct answer is D .