Chemistry Podcast

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)
HF
1.91
H2O
1.84
SO2
1.60
NH3
1.46
NF3
0.24
CH3Cl
1.86
HCl
1.03
H2S
1.10
HBr
0.78
HI
0.38

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
Where,
                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
Molecule
Bond Order
Bond Length (pm)
Bond Dissociation Energy (kJ/mol)
F2
1
142
158
O2
2
121
498
N2
3
110
945

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


Saturday, 19 August 2017

Science Quiz : Acids and Bases Chemistry MCQs Part 18

Science Quiz : Acids and Bases Chemistry MCQs


Science Quiz by www.ChemistryNotesInfo.com

These are some of the random multiple question answers from Acids and Bases Chemistry...

1. OH- ion is called as:

Hydronium Ion
Hydroxide Ion
Hydrate Ion
Hydrogen Ion


2. Taste of acidic food is:

Sweet
Salty
Sour
Bitter


3. H+ Ion (Hydrogen Ion) is simply a:

Proton
Neutron
Electron
Hydroxide Ion


4. Bases increases concentration of what in water:

H+ Ion
OH- Ion
Both
None


5. Which of the acid from given below choice of acids is more dangerous:

Citric Acid
Carbonic Acid
Hydrochloric Acid
None of the above


6. Which of the given below statement about Alkalis is true:

They cannot neutralise acids
They are all insoluble
They are all acids
They are all bases


7. What happens to litmus paper in basic solutions:

Red litmus paper turns blue
Blue litmus paper turns red
Pink litmus paper turns Black
Black litmus paper turns blue


8. A liquid has a pH of 6.5, so this liquid is:

Weakly acidic
Weakly alkaline
Strongly acidic
Neutral


9. A liquid has a pH of 14, so this liquid is:

Weakly acidic
Weakly alkaline
Strongly acidic
Strongly basic


10. If a solution have pH of 9, then its H+ concentration is:

1 x 10-9 moles/liter
1 x 10-18 moles/liter
1 x 109 moles/liter
1 x 1018 moles/liter



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Sunday, 23 July 2017

What are the factors which favor formation of ionic bonds?

What are the factors which favour formation of Ionic Bonds?

These are the factors which favours formation of ionic bonds...
1. One of the atoms i.e. Metal atom must have low ionization energy, so that it can easily lose its electrons.
2. Other atoms i.e. Non-Metal atoms must have high electron affinity, so that it can hold the extra electrons.
3. One of the atoms i.e. Metal atom should be large in size.
4. Other atoms i.e. Non-Metal atoms should be small in size.
5. Lattice energy of the crystal should be high, means the electrostatic attraction between charged ions in the crystal should be high.
6. Anion and cation should have inert gas electronic configuration
7. The combining elements should differ by at least 1.9 in electronegativity.

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
Where,                       
            R = radius of nucleus,
            A = mass number,
            R0 = contestant = 1.4x10-13cm

Rate of Decayof radioactive substance

Where,
            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

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

Half Life Time (t1/2)

            t1/2 = 0.693/K
Where,
            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 
Also,
            Average life time (T) = 1.44 x Half-life (T1/2)
Where,
            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
Where,
            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
Where,
            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
Where,
            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

NOTE:

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