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3.4.1: Formal Charge and Oxidation State (Problems)

  • Page ID
    235759
  • PROBLEM \(\PageIndex{1}\)

    Determine the formal charge and oxidation state of each element in the following:

    a. HCl
    b. CF4
    c. PCl3

    Answer a

    FC: H: 0, Cl: 0

    OX: H: +1, Cl: -1

    Answer b

    FC: C: 0, F: 0

    OX: C: +4, F: -1

    Answer c

    FC: P: 0, Cl: 0

    OX: P: +3, Cl: -1

    PROBLEM \(\PageIndex{2}\)

    Determine the formal charge and oxidation state of each element in the following:

    a. H3O+
    b. \(\ce{SO4^2-}\)

    c. NH3
    d. \(\ce{O2^2-}\)

    e. H2O2

    Answer a

    FC: H: 0, O: +1

    OX: H: +1, O: -2

    Answer b

    FC: S: +2, O: -1

    OX: S: +6, O: -2

    Answer c

    FC: N: 0, H: 0

    OX: N: -3, H: +1

    Answer d

    FC: -1

    OX: -1

    Answer e

    FC: O: 0, H: 0

    OX: O: -1, H: +1

    Click here to see a video of the solution

    PROBLEM \(\PageIndex{3}\)

    Calculate the formal charge and oxidation state of chlorine in the molecules Cl2 and CCl4.

    Answer

    FC: Cl in Cl2: 0; Cl in CCl4: 0

    OX: Cl in Cl2: 0; Cl in CCl4: -1

    PROBLEM \(\PageIndex{4}\)

    Calculate the formal charge and oxidation state of each element in the following compounds and ions:

    a. F2CO
    b. NO
    c. \(\ce{BF4-}\)

    d. \(\ce{SnCl3-}\)
    e. H2CCH2
    f. \(\ce{PO4^3-}\)

    Answer a

    FC: C: 0, F :0, O: 0

    OX: C: +4, F: -1, O: -2

    Answer b

    FC: N: -1, O: 0

    OX: N: +1, O: -2

    Answer c

    FC: B: -1, F: 0

    OX: B: +3, F: -1

    Answer d

    FC: Sn: -1; Cl: 0

    OX: Sn: +2, Cl: -1

    Answer e

    FC: C: 0, H: 0

    OX: C: -2, H: +1

    Answer f

    FC: P: +1, O: -1

    OX: P: +5, O: -2

    PROBLEM \(\PageIndex{5}\)

    Based on formal charge considerations, which of the following would likely be the correct arrangement of atoms in nitrosyl chloride: ClNO or ClON?

    Answer

    ClNO

    Click here to see a video of the solution

    PROBLEM \(\PageIndex{6}\)

    Based on formal charge considerations, which of the following would likely be the correct arrangement of atoms in hypochlorous acid: HOCl or OClH?

    Answer

    HOCl

    PROBLEM \(\PageIndex{7}\)

    Based on formal charge considerations, which of the following would likely be the correct arrangement of atoms in sulfur dioxide: OSO or SOO?

    Answer

    OSO

    Click here to see a video of the solution

    PROBLEM \(\PageIndex{8}\)

    Draw the structure of hydroxylamine, H3NO, and assign formal charges; look up the structure. Is the actual structure consistent with the formal charges?

    Answer

    The structure that gives zero formal charges is consistent with the actual structure:

     

    A Lewis structure shows a nitrogen atom with one lone pair of electrons single bonded to two hydrogen atoms and an oxygen atom which has two lone pairs of electrons. The oxygen atom is single bonded to a hydrogen atom.

    PROBLEM \(\PageIndex{9}\)

    Which of the following structures would we expect for nitrous acid? Determine the formal charges:

    Two Lewis structures are shown, with the word “or” in between. The left structure shows a nitrogen atom single bonded to an oxygen atom with three lone pairs of electrons. It is also single bonded to a hydrogen atom and double bonded to an oxygen atom with two lone pairs of electrons. The right structure shows a hydrogen atom single bonded to an oxygen atom with two lone pairs of electrons. The oxygen atom is single bonded to a nitrogen atom which is double bonded to an oxygen atom with two lone pairs of electrons.

    Answer

    The first structure is the best structure. the formal charges are closest to 0 (and also the second structure does not give a complete octet on N)

     

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