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 171: When air is passed through alkaline pyrogallol and then over quicklime, the only gases left are? Options:
  A) nitrogen and carbondoxide
  B) the rare gases
  C) nitrogen and oxygen
  D) nitrogen and the rare gases
  E) nitrogen, carbonioxide and the rare gases
  Show Answer
  The correct answer is D .
• Question 172:

  The only metal that is anti-bacterial is?

  Options:
  A) Iron
  B) Sodium
  C) Alluminium
  D) Copper
  Show Answer
  The correct answer is D .
• Question 173: Alkanals can be distinguished from alkanones by the reaction with Options:
  A) sudan lll stain
  B) starch iodide paper
  C) lithium tetrahydrido aluminate (lll)
  D) fehling's solution
  Show Answer
  The correct answer is D .
• Question 174: A silicon -containing ore has 92% ²⁸Si, 5% ²⁹Si and 3% ³⁰Si. Calculate the relative atomic mass of the silicon. Options:
  A) 14.00
  B) 29.00
  C) 28.11
  D) 28.00
  Show Answer
  The correct answer is C .
• Question 175:

  A solution contains 20g of solute in 180g of solvent. If the solvent is water, what is the concentration of the solution in terms of mass by mass percentage

  Options:
  A) 11.%
  B) 22.2%
  C) 10%
  D) 20%
  Show Answer
  The correct answer is C .
• Question 176:

  Which of the following conditions will most enhance the spontaneity of a reaction?

  Options:
  A) $\mathrm{\Delta }$H is negative and greater than T$\mathrm{\Delta }$S
  B) $\mathrm{\Delta }$H is negative and $\mathrm{\Delta }$S = 0
  C) $\mathrm{\Delta }$H is positive and less than T$\mathrm{\Delta }$S
  D) $\mathrm{\Delta }$H is positive and equal to T$\mathrm{\Delta }$S
  Show Answer
  The correct answer is A .
• Question 177: 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 178: For a general equation of the nature xP + yQ ≈ mR + nS, the expression for the equilibrium constant is? Options:
  A) k (p)^x (Q)^y
  B) (p)^x (Q)^y / (R)^m (S)ⁿ
  C) (R)^m (S)ⁿ / (p)^x (Q)^y
  D) m(R) n (S) / x(P) y (Q)
  Show Answer
  The correct answer is C .
• Question 179:

  The number of molecules of Carbon(iv)Oxide produced when 10.0g of CaCO${}_3$ is treated with 0.2dm${}^3$ of 1 Mole of HCL in the equation

  CaCO${}_3$ + 2HCL $\to$ CaCl${}_2$  + H${}_2$ O + CO${}_2$  , is ?

  Options:
  A) 1.00 X 10${}^{23}$
  B) 6.02 X 10${}^{23}$
  C) 6.02 X 10${}^{22}$
  D) 6.02 X 10${}^{24}$
  Show Answer
  The correct answer is C .
• Question 180: The enzyme used in the hydrolysis of starch to dextrin and maltose is Options:
  A) amylase
  B) diastatse
  C) invertase
  D) zymase
  Show Answer
  The correct answer is B .