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 1:

  Consider the equation below:

  Cr${}_2$O${}_7^{2-}$ + 6Fe${}^{2+}$ + 14H${}^{+}$ $\to$ 2Cr${}^{3+}$ + 6Fe${}^{3+}$ + 7H${}_2$O.

  The oxidation number of chromium changes from

  Options:
  A) +5 to +3
  B) +6 to +3
  C) -2 to +3
  D) +7 to +3
  Show Answer
  The correct answer is B .
• Question 2: Which of the following results in the fall of acid rain Options:
  A) oxide of lead
  B) particulate matter
  C) oxides of carbon
  D) gaseous hydrocarbon
  Show Answer
  The correct answer is C .
• Question 3:

  The ratio of the initial to the final pressure of a given mass of gas is 1:1.5. Calculate the final volume of the gas if the initial volume was 300cm${}^3$ at the same temperature.

  Options:
  A) 120cm${}^3$
  B) 200cm${}^3$
  C) 450cm${}^3$
  D) 750cm${}^3$
  Show Answer
  The correct answer is B .
• Question 4:

  

  The I.U.P.A.C name for the compound

  Options:
  A) 2-methyl-3-pentene
  B) 4-methyl-2-pentane
  C) 2-methyl-2-pentene
  D) 4-methylpent-2-ene
  E) 2-methyl-3-pentane
  Show Answer
  The correct answer is D .
• Question 5:

  The general formula for the Alkanals is?

  Options:
  A) R${}_2$CO
  B) RCHO
  C) ROH
  D) RCOOR
  Show Answer
  The correct answer is B .
• Question 6: The efficiency of petrol as a fuel in high-compression internal combustion engines improves with an increase in the amount of? Options:
  A) branched chain alkanes
  B) straight chain alkanes
  C) cycloalkanes
  D) halogenated hydrocarbons
  Show Answer
  The correct answer is A .
• Question 7: 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
  Show Answer
  The correct answer is D .
• Question 8: What is the consequences of increasing pressure on the equilibrium reaction ZnO_(s) + H_2(g) Zn_(s) + H₂O_(I)? Options:
  A) The equilibrium is driven to the left
  B) The equilibrium is driven to the right
  C) There is no effect
  D) More ZnO is produced
  Show Answer
  The correct answer is C .
• Question 9: The characteristics reaction of carbonyl compounds is? Options:
  A) substitution
  B) elimination
  C) addition
  D) saponfication
  Show Answer
  The correct answer is C .
• Question 10: When a few drops of water is added to a blue anhydrous cobalt (II) chloride, the colour changes to Options:
  A) white
  B) pink
  C) red
  D) blue
  Show Answer
  The correct answer is B .