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 631: Sugar is separated from its impurities by Options:
  A) precipitation
  B) crystallization
  C) distillation
  D) evaporation
  Show Answer
  The correct answer is B .
• Question 632: Which quantum number divides shells into orbitals? Options:
  A) principal
  B) Arzimuthal
  C) Magnetic
  D) Spin
  Show Answer
  The correct answer is B .
• Question 633: The substance ZnO dissolves in sodium hydroxide solution and mineral acid solution to give soluble products in each case. ZnO is therefore referred to as Options:
  A) an allotropic oxide
  B) an amphoteric oxide
  C) a peroxide
  D) a dioxide
  Show Answer
  The correct answer is B .
• Question 634:

  Which of these sources of water may likely contain the least concentration of Ca${}^{2+}$ and Mg${}^{2+}$?

  Options:
  A) Spring water
  B) River water
  C) Tap water
  D) Sea water
  Show Answer
  The correct answer is C .
• Question 635:

  For the reaction NH₄NO₂ $\to$ N₂ + 2H₂O, calculate the volume of nitrogen that would be produced at S. T. P from 320 g of the dioxonitrate(iii)salt. (Relative atomic masses: N = 14, O = 16, H = 1)

  Options:
  A) 2.24 dm ³
  B) 224 dm³
  C) 1.12 dm ³
  D) 112 dm ³
  E) 4.48 dm ³
  Show Answer
  The correct answer is D .
• Question 636: Which of the following metals is purified commercially by electrolysis? Options:
  A) Zn
  B) Fe
  C) Sn
  D) Cu
  Show Answer
  The correct answer is D .
• Question 637:

  

  The diagram above (Fig.3) shows the energy profile for the reaction A + B + = C + D From this diagram, it is clear that the reaction is

  Options:
  A) spontaneous
  B) isothermal
  C) adiabatic
  D) exothermic
  E) endothermic
  Show Answer
  The correct answer is D .
• Question 638:

  Which of the following is a primary constituent of crude oil?

  Options:
  A) Pentane
  B) Ethanol
  C) Heptane
  D) Methane
  Show Answer
  The correct answer is D .
• Question 639: In the course of purifying water for town supply the water is passed through large settlings tanks, containing sodium aluminate (III) to remove Options:
  A) large particles
  B) germs
  C) fine particles
  D) odour
  Show Answer
  The correct answer is A .
• Question 640: 300 cm³ of gas has a pressure of 800 mmHg. If the pressure is reduced to 650 mmHg, find its volume Options:
  A) 243.75 cm³
  B) 369.23 cm³
  C) 738.46 cm³
  D) 1733.36 cm³
  Show Answer
  The correct answer is B .