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ENSTP: Chemistry Lessons: ATOMIC AND ELECTRONIC STRUCTURE Topics

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  • Aug. 19, 2023, 2:50 p.m.
    NKENFACK BLONDEL

    CORRECTION

  • Aug. 15, 2023, 3:44 p.m.
    NKENFACK BLONDEL

    Option C) states that “there is entropy variation when there is heat exchange.” This statement is not necessarily incorrect, as there can indeed be a change in entropy when there is heat exchange between a system and its surroundings. However, the question specifically refers to an adiabatic process, which means that there is no heat exchange between the system and its surroundings. In this case, option C) is not relevant to the situation described in the question.

    In an adiabatic and irreversible expansion of an ideal gas, there is always a change in entropy due to the irreversibility of the process, even if there is no heat exchange with the surroundings. So, the correct answer to the question is option A) “there is always entropy variation.”

     

  • Aug. 15, 2023, 5:11 a.m.
    NKENFACK BLONDEL

    Momentum is conserved in an isolated system, but the question you asked was about an isolated system where only one quantity is always conserved. In this case, the correct answer is A) Energy. The law of conservation of energy states that the total energy of an isolated system remains constant over timeThis means that energy can neither be created nor destroyed, but can only be transformed or transferred from one form to another.

    On the other hand, the conservation of momentum is a major law of physics which states that the momentum of a system is constant if no external forces are acting on the systemIt is embodied in Newton’s First Law or The Law of InertiaThis means that the total momentum of an isolated system will remain constant as long as there are no external forces acting on it.

    In summary, both energy and momentum can be conserved in an isolated system, but the question specifically asked for only one quantity that is always conserved in an isolated system, and the correct answer to that question is A) Energy.

     

  • Aug. 9, 2023, 5:56 p.m.
    NKENFACK BLONDEL

    The carbon-fluorine bond is stronger than the carbon-oxygen bond. The bond dissociation energy (BDE) of a carbon-fluorine bond can be up to 130 kcal/mol, which is higher than other carbon-halogen and carbon-hydrogen bonds1. On the other hand, the C-O bond strength is also larger than C-N or C-C. For example, bond strengths are 91 kilocalories (380 kJ)/mol (at 298 K) in methanol2. This means that the carbon-fluorine bond is stronger than the carbon-oxygen bond.

    HENCE C IS THE CORRECT OPTION

     

  • Aug. 9, 2023, 5:24 p.m.
    NKENFACK BLONDEL

    CORRECTION:

    Charge density is the ratio of the charge of an ion to its volume. The charge density of an ion is determined by its size and charge. The smaller the ion and the greater its charge, the higher its charge density will be. Oxygen and sulfur are both in group 16 of the periodic table, and they both commonly form ions with a -2 charge. However, sulfur has a larger atomic radius than oxygen1, which means that its volume is larger. As a result, the charge density of sulfur is lower than that of oxygen.

    HENCE BY CONCLUSION THE CORRECT ANSWER IS D

     

  • Aug. 9, 2023, 2:26 a.m.
    NKENFACK BLONDEL

    CORRECT OPTION IS

  • Aug. 2, 2023, 3:52 p.m.
    NKENFACK BLONDEL

    here the answer is D

     

    • Aug. 5, 2023, 11:56 a.m.
      tandutabi

      D

    • Aug. 23, 2023, 4:38 p.m.
      ARNAUD

      YES YOU ARE CORRECT

  • Aug. 2, 2023, 3:38 p.m.
    NKENFACK BLONDEL

    Hello madam, 

    correction: intramolecular forces are attractive forces that holds atoms together witin a molecule or a substance. The are stronger and are usually called chemical bonds.

    intermolecular are weaker attractive forces that exist between molecules.

    there are not clear-cut guidlines for which intramolecular forces are strongest because they vary widely interms of stength.

    1)ionic bonds= attraction between cations and anions e.g Na-cl

    2)covalend bond= between shared pairs of electrons  and the nuclie e.g  F-H 

    3)metallic bonds= ATTRACTIVE BETWEEN SEA OF DELOCALISED ELECTRONS e.g Fe-Fe

    intermolecular  can vary alot too, but there are some more recongnized patterns

    1)ion dipole-dipole

    2)hydrogen bonds

    3)vandawall forces

     

Instructors

  • Ecole Normale Supérieure des Travaux Publics

  • Ecole Normale Supérieure des Travaux Publics

  • Ecole Normale Supérieure des Travaux Publics

  • Post Graduate School of Science and Technology, University of Dschang.

  • 2nd year medical student at the FACULTY OF MEDICINE AND BIOMEDICAL SCIENCE YAOUNDE.

  • 3ND year medical student at the FACULTY OF MEDICINE AND BIOMEDICAL SCIENCE YAOUNDE.


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