Chemistry Podcast

Showing posts with label Chemistry Formulas. Show all posts
Showing posts with label Chemistry Formulas. Show all posts

Sunday, 27 August 2017

Chemistry Formulas for Chemical Bonding

Chemistry Formulas for Chemical Bonding

   1.       Necessary condition for an ionic solid to be dissolved in water
                                Hydration Energy > Lattice Energy
   2.       Order of melting and boiling points of certain compounds
NaF > NaCl > NaBr > NaI;    MgO > CaO > BaO
3.       No Bond is 100% Ionic
4.       Force of attraction between two oppositely charged ions in vacuum (air) as per Coulombs Law
F = q1q2/r2
5.       Order of the Lattice Energy of some compounds
·         LiX > NaX > KX > RbX > CsX    (where X = F, Cl, Br, I)
·         MgO > CaO > SrO > BaO
·         MgCO3 > CaCO3 > SrCO3 > BaCO3
·         BaSO4 > SrSO4 > CaSO4 > MgSO4  
·         Mg(OH)2 > Ca(OH)2 > Sr(OH)2 > Ba(OH)2
·         Bivalent Ions-Bivalent Ions > Univalent Ions-Bivalent Ions or Bivalent Ions-Univalent Ions > Univalent Ions- Univalent Ions
6.       Example of some compounds which contains more than one type of bond
·         NaOH, KOH, Na2CO3  (Ionic Bond, Covalent Bond)
·         CO, NH3.BF3, [Co(NH3)3Cl3]  (Dative Bond, Covalent Bond)
·         NH4Cl, CuSO4, K4[Fe(CN)6], [Cu(NH3)4]SO4  (Dative Bond, Ionic Bond, Covalent Bond)
·         CuSO4.5H2O  (Hydrogen Bond, Dative Bond, Ionic Bond, Covalent Bond)
7.       Double bond or triple bond is always shorter than corresponding single bond
8.       As S-Orbital is smaller than P-Orbital so bond length decrease with increase in S-character
SP3  C-H  =  1.093 Å (as in Alkanes)
SP2  C-H  =  1.087 Å (as in Alkenes)
SP  C-H  =  1.057 Å (as in Alkynes)
9.       Bond length increases if size of bonded atom is increases with given atom
HI > HBr > HCl > HF
10.   Bond distance is directly proportional to Atomic size
11.   Order of bond strength (or bond energy) of different hydrogen halides
H-F > H-Cl > H-Br > H-I
12.   Bond energy is directly proportional to bond order
Triple Bond > Double Bond > Single Bond
13.   Formula of Dipole Moment
Dipole moment (µ) = Electronic Charge (e) x Distance (d)
14.   Unit of Dipole Moment
Debye (D)
1D = 1 x 10-18e.s.u. cm
SI unit of Dipole Moment is = Coulomb-Meter (C-m)
1D = 3.336 x 10-30 C-m
15.   Dipole Moment of some substances
Substance with Formula
Dipole Moment (D)

16.   Formula to calculate percentage ionic character of covalent bond
% Ionic Character = (Observed dipole moment x 100)/Dipole moment for 100% ionic bond
17.   Order of polarizing power of cations
Li+ > Na+ > K+ > Rb+ > Cs+
Be2+ > Mg2+ > Ca2+ > Sr2+ > Ba2+
Al3+ > Mg2+ > Na+
18.   Order of polarizing power of anions
N3- > O2- > F-
P3- > S2- > Cl-
19.   Chemistry Formula of Bond Order
Bond Order = [Nb-Na]/2
                Na = Number of electrons in antibonding molecular orbitals
                Nb = Number of electrons in bonding molecular orbitals
20.   Some molecules with their bond order, bond length and bond dissociation energy
Bond Order
Bond Length (pm)
Bond Dissociation Energy (kJ/mol)

21.   Bond Order in compounds which exhibits Resonance
Bond Order = (Total No. of bonds between two atoms)/(Total No. of resonating structures)

Sunday, 16 July 2017

Chemistry Formulas for Nuclear Chemistry (Radioactivity)

Chemistry Formulas for Nuclear Chemistry (Radioactivity)

Empirical relationship between size of nucleus and its mass number is
            R = R0A1/3
            R = radius of nucleus,
            A = mass number,
            R0 = contestant = 1.4x10-13cm

Rate of Decayof radioactive substance

            K = decay constant,
            N = No. of atoms,
            t = time of decay,
            dN = small fraction of N,
            dt = small fraction of t

Value of Decay Constant

            N0 = No. of atoms originally present,
            N = No. of atoms present after time t

Half Life Time (t1/2)

            t1/2 = 0.693/K
            K = decay constant

Average Life Time (T)

            Average life time (T) =Sum of the lives of the nuclei/ Total number of nuclei
            T = 1/K 
            Average life time (T) = 1.44 x Half-life (T1/2)
            K = decay constant
            T = Average Life Time
            T1/2 = Half Life

Specific Activity

            Specific Activity = Rate of decay/m
                                      = KN/m
                                      = K x Avogadro Number/ Atomic Mass in gram
            N = Number of Radioactive nuclei that undergoes disintegration

Units of Radioactivity

            Standard unit of radioactivity is curie (c).
            1c = Activity of 1gram Ra226 = 3.7 x 1010dps
            dps = disintegrations per second
millicurie (mc) = 3.7 x 107dps
microcurie (µc) = 3.7 x 104dps
Other units of radioactivity are Rutherford (rd) and Becquerel (Bq).

Rutherford (rd)

1rd = 106dps

Becquerel (Bq)

            Becquerel (Bq) is the SI unit of radioactivity.
                        1Bq = 1 disintegrations per second
                        1 Bq = 1 dps

Radioactive Equilibrium

            A ----à B ----à C
            At steady state,
                        NA/NB = KB/KA = TA/TB
            KA = radioactivity constant for the process A---àB
            KB = radioactivity constant for the process B---àC
            TA = average life period of A
            TB = average life period of B
Radioactive Equilibrium in terms of half-life periods,
            NA/NB = (T1/2)A/ (T1/2)B

Sunday, 21 May 2017

Chemistry Formula for Atomic Structure Part 2

Chemistry Formulas for Atomic Structure

Chemistry Formulas from Bohr’s Model of Atom

·         Angular momentum of electron in nth orbit

Where, m = Mass of the electron,
            v = velocity of electron,
            r = radius of the orbit,
            h = Planck’s constant,
            n = no. of orbit in which electron is present,

·         Energy of electron in nth orbit

           Where, Z = Atomic No. of Electron,

·         Energy absorbed or released in an electron jump ( E)


·         Radius of orbits of hydrogen like species

         For hydrogen atom Z = 1, for first orbit n = 1,
         On substituting values of the constants
         h = 6.62x10-27erg sec,
         m = 9.1x10-28g,
         e = 4.8x10-10
     we get,
    r = 0.529 Å
So, radius of first orbit of hydrogen atom is 0.529 Å.

·         Radius of nth orbits of hydrogen like species

rn = 0.529n2/Z Å

·         Velocity of electron in nth orbit

      On substituting values of the constants
      We get,

·         No. of revolution per second made by an electron around the nucleus of atom

·         Energy of electron in nth orbit (En)

        On substituting values of the constants
        We get,          
         In general,

·         Energy of electron in a Hydrogen Atom in different energy levels

Energy Level
E (Joules/atom)
E (eV/atom)
E (kcal/mol)

·         Frequency or wave length of emitted radiation

            Where, λ = wavelength of emitted radiations
                        R = Rydberg constant for Hydrogen atom

·         Number of spectral lines produced when an electron drops from nth level to ground level


Chemistry Formulas from Photoelectric Effect

·         Planck’s Relationship,

E = hv

·         Total energy,

Total Energy = (mv2/2) + w
Where, w = energy required to remove the electron.

Chemistry Formulas from Wave Mechanical Concept of Atom

·         De Broglie’s Equation,

          Where, m = mass of particle,
                        v = velocity of the particle,
                        h = Planck’s Constant,

Chemistry Formulas from Heisenberg’s Uncertainty Principle

·        Heisenberg’s Uncertainty Principle,

           Where,   = uncertainty in the position of the particle,
                        = uncertainty in the momentum of the particle,

Chemistry Formulas from Quantum Numbers

·         Principle Quantum Number (n),

Maximum no. of electrons in n principle quantum number = 2n2

·         Azimuthal Quantum Number (l),

For the given value of principle quantum number (n), azimuthal quantum number (l), may have all integral values from 0 to (n-1)

·         Magnetic Quantum Number (m),

No. of orbitals in a sub-shell = 2 l +1

·         Spin Quantum Number (s),

For spinning of electron about its own axis


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