Nothing Special   »   [go: up one dir, main page]
Scribd Logo
Upload

Welcome to Scribd!

  • 44 views

    CHEMICAL BONDING Notes

    Uploaded by

    P Y
    1. Hydrogen bonding occurs between a hydrogen atom covalently bonded to a highly electronegative atom like N, O, or F and another highly electronegative atom. This causes hydrogen bonds to be stronger than van der Waals forces but weaker than covalent bonds. 2. Each water molecule can form an average of two hydrogen bonds with other molecules. This extensive hydrogen bonding network accounts for water's unusually high boiling point compared to other hydrogen bonding molecules like HF and NH3 which form fewer hydrogen bonds per molecule. 3. Hydrogen bonding increases the boiling points and solubility of compounds in water, and causes carboxylic acids to exist as dimers in the vapor phase with two molecules linked

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd

    CHEMICAL BONDING Notes

    Uploaded by

    P Y
    44 views19 pages
    1. Hydrogen bonding occurs between a hydrogen atom covalently bonded to a highly electronegative atom like N, O, or F and another highly electronegative atom. This causes hydrogen bonds to be stronger than van der Waals forces but weaker than covalent bonds. 2. Each water molecule can form an average of two hydrogen bonds with other molecules. This extensive hydrogen bonding network accounts for water's unusually high boiling point compared to other hydrogen bonding molecules like HF and NH3 which form fewer hydrogen bonds per molecule. 3. Hydrogen bonding increases the boiling points and solubility of compounds in water, and causes carboxylic acids to exist as dimers in the vapor phase with two molecules linked

    Original Description:

    Original Title

    CHEMICAL BONDING notes

    Copyright

    © © All Rights Reserved

    Available Formats

    PPTX, PDF, TXT or read online from Scribd

    Did you find this document useful?

    Is this content inappropriate?

    1. Hydrogen bonding occurs between a hydrogen atom covalently bonded to a highly electronegative atom like N, O, or F and another highly electronegative atom. This causes hydrogen bonds to be stronger than van der Waals forces but weaker than covalent bonds. 2. Each water molecule can form an average of two hydrogen bonds with other molecules. This extensive hydrogen bonding network accounts for water's unusually high boiling point compared to other hydrogen bonding molecules like HF and NH3 which form fewer hydrogen bonds per molecule. 3. Hydrogen bonding increases the boiling points and solubility of compounds in water, and causes carboxylic acids to exist as dimers in the vapor phase with two molecules linked

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    44 views19 pages

    CHEMICAL BONDING Notes

    Uploaded by

    P Y
    1. Hydrogen bonding occurs between a hydrogen atom covalently bonded to a highly electronegative atom like N, O, or F and another highly electronegative atom. This causes hydrogen bonds to be stronger than van der Waals forces but weaker than covalent bonds. 2. Each water molecule can form an average of two hydrogen bonds with other molecules. This extensive hydrogen bonding network accounts for water's unusually high boiling point compared to other hydrogen bonding molecules like HF and NH3 which form fewer hydrogen bonds per molecule. 3. Hydrogen bonding increases the boiling points and solubility of compounds in water, and causes carboxylic acids to exist as dimers in the vapor phase with two molecules linked

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    of 19

    HYDROGEN BONDING

    1. Hydrogen bonding is a type of dipole-dipole


    attraction between a hydrogen atom which is
    covalently bonded to a very highly electronegative
    atom (N, O, F) and another atom that is also very
    highly electronegative atom such as (N, O, F).
    2. Example: H2O, NH3 HF

    1
    Hydrogen bonds are stronger than Van der
    Waals forces. It is about one tenth as strong as
    covalent bonds. But weaker than covalent bond

    2
    HYDROGEN BONDING
    1. To form a hydrogen bond, we need a hydrogen
    atom and a lone pair of electrons.
    2. For hydrogen flouride molecule, it can take part
    in two hydrogen bonds formation but forms an
    average of one hydrogen bond per molecule.
    Hydrogen bond
    Covalent bond

    3
    HYDROGEN BONDING
    1. To form a hydrogen bond, we need a hydrogen
    atom and a lone pair of electrons.
    2. Each water molecule can form an average of two
    hydrogen bonds

    Covalent bond
    Hydrogen bond

    4
    HYDROGEN BONDING
    1. To form a hydrogen bond, we need a hydrogen
    atom and a lone pair of electrons.
    2. Each ammonia molecule can form an average of
    one hydrogen bond.
    Covalent bond

    Hydrogen bond

    5
    EXERCISE

    1. HF has exceptionally high boiling point compare to


    HCl, HBr and HI. Why
    H-F ; strong hydrogen bond exist

    2. Boiling point of HF is higher than NH3, Explain.


     F atom is more electronegative than N atom
     Hydrogen bonding in HF molecules is stronger than
    hydrogen bond in NH3

    6
    3. Boiling point of water is higher than the
    boiling point of HF. Explain.
    o Each oxygen atom in water molecules is able
    to form 2 hydrogen bonds with two other
    molecules.
    o Where as each fluorine atom in the HF
    molecule can form only one hydrogen bond.

    7
    HYDROGEN BONDING
    EFFECT OF HYDROGEN BONDING ON PHYSICAL
    PROPERTIES OF SUBSTANCES
    A. Boiling point
    B. Solubility of Covalent Compound in
    Water
    C. The molar mass of Carboxylic acid in vapour
    phase
    D. The density of solid water/ice

    8
    HYDROGEN BONDING
    1. BOILING POINT

    i. NH3, H2O and HF have an abnormally higher boiling point in


    respective groups. Explain.
    ii. NH3 has the lowest B.P compared to HF and H2O. Explain
    iii. B.P of water is higher than HF although fluorine is more
    electronegative than oxygen. Explain
    9
    HYDROGEN BONDING
    2. SOLUBILITY OF COVALENT COMPOUND IN WATER
    In general, covalent compounds are not soluble in
    water.
    Some covalent compounds are soluble in water
    because of
    a) reaction with water molecules or hydrogen bonding
    with water molecules.

    10
    Hydrogen bonding between ethanol, CH3CH2OH
    and water molecules.

    11
    Hydrogen bonding between ethanoic acid,
    CH3COOH and water molecules

    12
    Hydrogen bonding between methyl amine
    CH3NH2 and water molecules

    13
    HYDROGEN BONDING
    3. THE MOLAR MASS OF CARBOXYLIC ACIDS IN THE VAPOUR
    PHASE

    14
    Ethanoic acid and benzoic acid exist as dimers in
    organic solvent.
    Dimers are stable because two two molecules of
    carboxylic are linked together through two hydrogen
    bond. 15
    HYDROGEN BONDING
    4. THE DENSITY OF SOLID WATER/ICE – Ice is less dense than
    water
    a) Each water molecule in ice is hydrogen bonded to four other
    water molecules in a tetrahedral arrangement. This
    arrangement creates a very open three dimensional
    structure where the molecules are less closely packed than
    in the liquid state.

    Empty
    space

    16
    HYDROGEN BONDING
    b) When ice melts some of the hydrogen bonds break
    and the open structure of ice collapses.
    c) Hence the H2O molecules become more closely
    packed, thus giving water a greater density than ice.

    17
    HYDROGEN BONDING
    INTERMOLECULAR AND INTRAMOLECULAR HYDROGEN
    BONDING
    a) Intermolecular hydrogen bonds - Hydrogen bonds that
    occur between two different molecules (HF, NH3, H2O
    and CH3COOH)
    b) 4-nitrophenol is held by intermolecular hydrogen
    bonds. Its boiling point (279°C) is higher than 2-
    nitrophenol (216°C). The hydroxyl group of 4-
    nitrophenol is not close enough to the oxygen atom in
    the nitro group to form bond with them.

    4-nitrophenol
    2-nitrophenol
    18
    HYDROGEN BONDING
    INTERMOLECULAR AND INTRAMOLECULAR HYDROGEN
    BONDING
    b) Intramolecular hydrogen bonds – hydrogen bonds
    that occur within the same molecule.

    2-nitrophenol b.p(216°C) 4-nitrophenol(b.p 279°C)

    19

    You might also like