50 Hot Key Points to blast Jamb Chemistry

We bring you a new series on some Jamb Key points for Chemistry in Jamb, Waec and Post utme. These hot key points to blast Physics will help achieve the following:

• prepare for your Jamb, Waec and Post Utme examinations
• keep you updated on key points and likely questions that can be asked in these examinations
• help you cover up more grounds in your reading.

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50 Hot Key Points to blast Jamb Chemistry

Key Points on Jamb Chemistry hot topics (1 to 10)

1. 1. Air, Sea-water, Blood, Petroleum, Palm wine, Urine e.t.c are all mixtures as they cannot be represented by a chemical formula.
   2. Alloys are also mixtures, they are a mixture of two or more metals.
   3. To know if a substance is a compound, simply ask yourself if that substance has a chemical formula
   4. Water, acids, alkalis, limestone, sugar, salt are examples of compound
   5. Sieving is a separating technique that uses different in sizes of the mixture as its principle of separation.
   6. Filtration is a separating technique that is used for separating insoluble solid from the liquid using a filter.
   7. Evaporation is a separating technique used for separating the solute in a solution from its solvent by heating.
   8. It should be noted that Evaporation technique is used only when the solute to be separated is not affected by the heat(that is, the solute do not decompose on heating)
   9. Crystallization is used to separate the solute in a solution from its solvent through repeated heating and cooling of the mixture.
   10. It should be noted that crystallization is used when the solute(solid) to be separated will decompose on heating. Most ammonium salt and trioxonitrate salt uses crystallization as there method of separation.
       

       Jamb Key Points for Chemistry (11 to 20)

   11. Fractional crystallization is used to separate different solutes(solids) from a solution based on their differences in solubility at different temperature. The salt with the least solubility crystalizes out first.
   12. Fractional distillation is used to separate different solvent in a mixture based on their difference in boiling point.
   13. The Separating funnel is used to separate a mixture of two or more immiscible liquids.
   14. Precipitation is used to separate insoluble solid(principle of solubility) from two miscible liquid.
   15. Chromatography is a separating technique that separates a mixture of solvent-based on their different rate of movement in a medium.
   16. Sublimation is used to separate a solid that sublimes on heating(that is, the solid turns directly into vapour on heating) from its mixture. A good example of solid that sublimes on heating is the Ammonium chloride NH_{4}ClNH4​Cl
   17. The presence of impurities in a liquid increases the boiling point of the liquid (This means that if impurities are added to water the water will boil at a temperature higher than 100 probably 115).
   18. The presence of impurities in a solid reduces its melting point of the solid (This means that if the impurity is present in ice, the melting point will not be 0 degrees rather it will be something lower probably –10 degrees)
   19. Magnetic separation is used to separate iron or ferrous metals from a mixture
   20. A mixture of iron filings and sand can be best separated using magnetic separation

Jamb Key Points for Chemistry (21-30)

1. 1. The law of conservation of mass states that matter can never be created nor destroyed
   2. The law which states that all pure samples of a particular pure chemical substance contain the same elements combined in the same proportion by mass is the law of definite proportion.
   3. The law of definite proportion is also called the law of constant composition
   4. Electrons, Protons, Neutrons are all sub-atomic particles
   5. J.J Thompson discovered electrons using the cathode-ray tubes
   6. J.J Thompson discovered positively charge particles(protons) by using cathode ray tube with one of its plate perforated
   7. Chadwick discovered neutrons by bombarding beryllium metal with alpha particles
   8. J.J Thompson proposed that an atom is a sphere containing positive and negative particle homogenously distributed in the sphere
   9. Although J.J Thompson model of the atom could explain the neutrality of atoms, it could not explain Rutherford Scattering experiment, It could not also explain the presence of a nucleus in an atom
   10. Ernst Rutherford discovered protons by bombarding alpha particle on thin gold foil. He studied the deflection pattern of the alpha particle he bombarded on the foil.

Likely Jamb Chemistry questions to note(31-40)

1. 1. Rutherford proposed that an atom is made of up a very dense positively charged nucleus which contains the protons and neutrons while the electrons orbits nucleus.
   2. The Rutherford model of an atom is sometimes called Rutherford Planetary Model or The Plum Pudding Model
   3. Ernst Rutherford model of an atom could not explain the stability of atoms and did not mention anything about the arrangement of electrons in orbit.
   4. Neil Bohr atomic model theory posits that electrons revolve around the nucleus of an atom at a discrete or quantized energy level with fixed energy
   5. Neil Bohr atomic model could explain the stability of atoms.
   6. The Major drawback of Bohr’s model was that it could only explain hydrogen atoms
   7. The Electron Cloud Model proposed by Erwin Schrödinger and Werner Heisenberg was the best theory that could explain the behaviour of atoms.
   8. The electron cloud model says that we cannot know exactly where an electron is at any given time, but we can only know the probability of an electron present in a particular location
   9. Elements are arranged on the periodic table based on their atomic number
   10. The atomic number of an element is the number of protons in the nucleus of that atom

Hot 2019 key points in chemistry(41-50)

1. The atomic mass of an element is the sum of its protons and neutrons in the nucleus of the atom. ATOMIC MASS = NO OF PROTONS + NO OF NEUTRONS
2. Isotopes are elements with the same atomic number(same number of protons) and different mass number(Due to the difference in the number of neutrons)
3. The isotopes of Hydrogen are: Hydrogen ^{1}_{1}H, Deuterium ^{2}_{1}H (also known as heavy water) and Tritium ^{3}_{1}H11​H,Deuterium12​H(alsoknownasheavywater)andTritium13​H
4. Tritium which is an isotope of Hydrogen is radioactive.
5. Chlorine exhibit isotopy. The two major isotopes of chlorine are Chlorine-35 and chlorine-37.
6. Oxygen exhibit isotopy. Oxygen has three stable isotopes ^{16}O, ^{17}O, ^{18}O16O,17O,18O
7. Helium exhibit isotopy and has two stable isotopes; ^3He,^{4}He3He,4He
8. Sulphur exhibit isotopy and has 4 stable isotopes ^{32}S,^{33}S,^{34}S,^{36}S32S,33S,34S,36S
9. Uranium exhibit isotopy its isotopes are: Uranium-235 and Uranium-238^{235}U,^{238}U235U,238U
10. Nitrogen exhibit isotopy it has two stable isotopes which are: Nitrogen-14 and Nitrogen-13 ^{14}N,^{15}N14N,15N

 

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