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 2041: The enzymes responsible for converting sucrose into two simple isomeric sugars is Options:
  A) maltase
  B) amylase
  C) invertase
  D) lactase
  Show Answer
  The correct answer is C .
• Question 2042: The colour of litmus in an alkaline medium is Options:
  A) Red
  B) Yellow
  C) Pink
  D) Blue
  Show Answer
  The correct answer is D .
• Question 2043: An oxide XO₂ has a vapour density of 32. What is the atomic mass of X? Options:
  A) 32
  B) 20
  C) 14
  D) 12
  Show Answer
  The correct answer is A .
• Question 2044: When a pressure cooker is half filled with water, and heated to boiling point, then the pressure inside the cooker will? Options:
  A) decrease, since only a fraction of the water molecules has changed to vapour
  B) remain constant, because the total number of water molecules has not changed
  C) increase, because the water molecules can now reach every part of the sealed tube
  D) decrease, since water boils under reduced pressure
  E) increase, because the water vapour molecules now strike the walls of the tube more frequently because of their increased velocity
  Show Answer
  The correct answer is E .
• Question 2045: A consequence of global warming is Options:
  A) air pollution
  B) water pollution
  C) increased humudity
  D) flooding
  Show Answer
  The correct answer is D .
• Question 2046: An efflorescent compound is a substance that? Options:
  A) absorbs water froom the air without dissolving in it
  B) is capable of giving off coloured luminosity
  C) gives out water to the atmosphere
  D) absorbs water from the air and dissolves in it
  E) gives out its water of crystallization on heating
  Show Answer
  The correct answer is C .
• Question 2047: Which of the following compounds of trioxonitrate (V) will decomposes to give dinitrogen (i) oxide and water when heated? Options:
  A) NaNO₃
  B) Zn(NO₃)₂
  C) Cu(NO₃)₂
  D) NH₄NO₃
  Show Answer
  The correct answer is D .
• Question 2048:

  For the general equation of the nature

  XP + yQ ⇌ mR + nS, the expression for the equilibrium constant is

  Options:
  A) k[P]${}^x$[Q]${}^y$
  B) $\frac{m[R][S]}{x[P]y[Q]}$
  C) $\frac{[P{]}^x[Q{]}^y}{[R{]}^m[S{]}^n}$
  D) $\frac{[R{]}^m[S{]}^n}{[P{]}^x[Q{]}^y}$
  Show Answer
  The correct answer is D .
• Question 2049:

  A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen. If the molar mass of the compound is 180. Find the molecular formula.

  [H = 1, C = 12, O = 16]

  Options:
  A) C${}_3$H${}_6$O${}_3$
  B) C${}_6$H${}_6$O${}_3$
  C) C${}_6$H${}_{12}$O${}_6$
  D) CH${}_2$O
  Show Answer
  The correct answer is C .
• Question 2050:

  In the reaction:

  2Hl_(g) ↔ H_2(g) + l_2(g)' ΔH = 10 kj;

  The concentration of iodine in the equilibrium mixture can be increased by?

  Options:
  A) raising the pressure
  B) raising the temperature
  C) adding a catalyst
  D) lowering the pressure
  Show Answer
  The correct answer is B .