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 831: What weight of sodium hydroxide is required to make 500 cm³ of 0.2 M solution?(Na = 23, O = 16, H = 1) Options:
  A) 40 g
  B) 20 g
  C) 10 g
  D) 4 g
  E) 2 g
  Show Answer
  The correct answer is D .
• Question 832:

  A colored gas that is known to be poisonous and can readily damage the mucous liningof the lungs is?

  Options:
  A) hydrogen sulphide
  B) carbon(ii)oxide
  C) chlorine
  D) sulphur(iv)oxide
  Show Answer
  The correct answer is C .
• Question 833:

  Elements X and Y have electronic configurations 1s${}^2$2s${}^2$2p${}^4$ and 1s${}^2$2s${}^2$2p${}^6$3s${}^2$3p${}^1$ respectively. When they combine, the formula of the compound formed is

  Options:
  A) XY
  B) X${}_2$Y
  C) Y${}_2$X${}_3$
  D) X${}_2$Y${}_3$
  Show Answer
  The correct answer is C .
• Question 834: Electronic configuration of an elements 13x in the subsidiary energy level is Options:
  A) $1s^{2}2s^{2}2p^{6}3s^{2}3p^1$
  B) $1s^{2}2s^{2}2p^{4}3p^{1}3s^1$
  C) $1s^{2}2s^{2}2p^{6}3s^{2}3p^3$
  D) $1s^{1}2s^{2}2p^{6}3s^{2}3p^4$
  Show Answer
  The correct answer is A .
• Question 835: Commercial bleaching can be carried out using Options:
  A) sulphur (IV) oxide and ammonia
  B) hydrogen sulphide and chlorine
  C) chlorine and sulphur (IV) oxide
  D) ammonia and chlorine
  Show Answer
  The correct answer is C .
• Question 836: Which of the following represents a precipitation reaction? Options:
  A) H₂SO₄ + NaCl $\to$ NaHSO₄ + HCl
  B) Fe +H₂SO₄ $\to$ FeSO₄ + H₂
  C) 4HCl + MnO₂ $\to$ MnCl₂ + 2H₂O + Cl₂
  D) Na₂SO₄ + pb(NO₃) $\to$ PbSO₄ + 2NaNO
  E) CuO +2HCl $\to$ Cl₂ + H₂O
  Show Answer
  The correct answer is D .
• Question 837: Due to the unstable nature of ethyne, it is stored by dissolving in Options:
  A) ethane-1,2-diol
  B) propanol
  C) ethanoic acid
  D) propanone
  Show Answer
  The correct answer is D .
• Question 838: A given quantity of a gas occupies a volume of 228 cm³ at a pressure of 750mm Hg. What will be its volume at atmospheric pressure? Options:
  A) 220 cm³
  B) 225 cm³
  C) 230 cm³
  D) 235 cm³
  Show Answer
  The correct answer is B .
• Question 839: The oxidation number of boron in NaBH ₄ is Options:
  A) -3
  B) -1
  C) +1
  D) +3
  Show Answer
  The correct answer is D .
• Question 840:

  If 30cm³ of oxygen diffuses through a porous pot in 7 seconds, how long will it take 60cm³ of chlorine to diffuse through the same pot, if the vapour densities of oxygen and chlorine are 16 and 36 respectively?

  Options:
  A) 9.3 sec
  B) 14 sec
  C) 21 sec
  D) 28 sec
  E) 30.3 sec
  Show Answer
  The correct answer is C .