Formulas of acid and base

Formulas of acid and base


 List the formulas of  acid and base

Hello friends, welcome to blog, today we are going to discuss and list the formula's of acid and base.
The earlier classification of substances into acid and base according to their characteristics and properties. For example an acid is a substance  with the sour taste and turns blue Litmus to red also liberate hydrogen with active metal like sodium, potassium, calcium etc.
A base is a substance with the bitter taste and turns red litmus to blue and have a soap touch.For example NaOH , KOH etc.


Various theories and modern concept explain acid and base are based on the structure and composition. Three theories concept's explain the acidic and basic character of a substance. These are Arrhenius concept, bronsted lowry concept and Lewis concept.

These theories helps to identify  a substance whether it is a strong or weak acid / base.

In 1884 an Arrhenius  proposed the theory of acid and base. According to this,

Acids

  Acids are substances which produce(dissociates) hydrogen ion(H+) when mixed with water.It has its own chemical properties and characteristics when react others.
For example:-
                       

Base

  Base are substances which produce(dissociates) hydroxide ion(OH-) when mixed with water.
Note:-
 While studying remember "properties of Acids and Bases" all bases do not dissolve in water. An alkali is a base that dissolves in water. Common alkali's are NaOH Sodium hydroxide KOH Potassium hydroxide
For example:-
 

what is the formula for hydrofluoric acid- HF
phosphorous acid formula-H3PO4
hydrobromic acid formula-HBr


Properties of acids and bases

Properties of acids and bases

Properties of acids and bases

Properties of acids and bases: The classification of substances into acid and base is according to some of their characteristics.

how can you tell an acid from a base

We can classify properties of acid and base
1.Physical methods
2.Chemical methods

Physical Properties Acids and Bases

The substances that taste sour are called as acid. For example lemon juice, tomato, curd.
The substances that taste bitter are called as base.For example soap, lime water containing calcium hydroxide, house cleaners.

Some Naturally occurring acids

 Vinegar                     – Acetic Acid
 Orange                      – Citric Acid
 Lemon                      – Citric Acid
 Tamarind                  – Tartaric Acid
 Tomato                      – Oxalic Acid
 Sour milk (Curd)       – Lactic Acid
 Ant and Nettle sting          – Methanoic Acid

Acid-Base Indicators

             Name of the                             Colour Change                             Colour Change
                Indicator                                   withAcid                                        with Base


A.      Blue litmus solution                          To red                                          No change
B.      Red litmus solution                            No change                                   To blue
C.      Turmeric                                             No change                                   To red
D.      Methyl orange                                    To red                                          To yellow
E.      Phenolphthalein (colourless)               No change                                  To pink

Chemical Properties of Acids and Bases

1. Acid + Metal → Salt + Hydrogen

Pop test : When a burning candle is brought near a test tube containing hydrogen gas it burns with a ‘Pop’ sound. This test is conducted for examining the presence of hydrogen gas.

2. Base + Metal→ Salt + Hydrogen
      Note – Such reactions are not possible with all the metals.


3. Action of Acids with metal Carbonates and metal bicarbonates

Metal Carbonate + Acid → Salt + Carbondioxide + Water

4. Acids or bases in a Water Solution

   Acids produce H+ions in the presence of water
   Bases provide (OH–) ions in the presence of water

5. Reaction of Non Metallic Oxide with Base
   
     Non metallic oxide + Base →  Salt + Water

6.Reactions of metal oxides with acids

   Metal Oxide + Acid → Salt + Water

7. Neutralization Reactions 

     Base + Acid→ Salt + Water
Note:-
 While studying remember "properties of Acids and Bases" all bases do not dissolve in water. An alkali is a base that dissolves in water. Common alkali's are NaOH Sodium hydroxide KOH Potassium hydroxide












Chemistry Bond order|bond strength order|all Examples.

Chemistry Bond order|bond strength order|all Examples.

Bond order

Hello friends, welcome to our blog,today we are going to discuss the bond order, how to calculate it and what's its formula. The bond order can be calculated with the help of two concepts.
1. Lewis concept and
2. Molecular orbital theory(MOT)

According to Lewis concept , in a covalent bond, the bond order may be defined as:

 The number of bonds between the two atoms in a molecule. 

For example,

Bond order of H2(H−H bond) = 1           ;                  Bond order of O2 (O=O bond) = 2
Bond order of N2(N≡N bond)  =3            ;                 Bond order of (H−C≡C−H)
                                                                                                 carbon-carbon bond order= 3.
Note:

1.The Isoelectronic molecules and ions have identical bond orders
    For example, bond order of  N2 , CO and NO+  (all have 14 electrons) is 3.        

2. With the increasing bond order, the bond enthalpy increases and bond level decreases. For example,
 Bond order of N2 =3;Bond enthalpy = 945 KJ mol-1       
Bond order of O2 = 2;Bond enthalpy = 498 KJ mol-1     
Bond order of F2 =1;Bond enthalpy =  158 KJ mol-1
This video helps you how to write electronic configuration using MOT concept.
In case of Molecular orbital theory, the electron present in bonding molecular orbital is known as bonding electrons while electron present in antibonding molecular orbital is called antibonding electrons.
                

 Also, we have learnt that bonding molecular orbitals have lower energy as compared to antibonding molecular orbitals and greater stability. Thus, the molecular orbital stability  can be predicted in terms of electrons present in bonding molecular orbital( Na electrons)and those present in antibonding molecular( Nb electrons).The following generalisation can be made.

Stability

A. If Nb > Na ,the molecule is stable.
B. If Nb < Na ,the molecule is unstable.
C. If Nb = Na ,the molecule is unstable.

In fact, the bonding electrons tend to bring nuclei of the atomic orbital closer while the antibonding electrons tend to  push them apart. Thus, a stable  molecule will be formed only if Nb  electrons are more than Nelectrons.

Bond order Define

Half  of the difference between the number of electrons present in bonding and antibonding molecular orbitals.

Bond order formula

Thus,Bond order(B.O)=1/2[Nb -Na ] 
The Bond order may be whole number,fractional or even zero..It may also be positive or negative.    
If Bond Order = Positive, the molecule is stable.
If Bond Order = zero, the molecule is unstable or not exists.   
If Bond Order = Negative, the molecule is unstable.               

Hydrogen molecule(H2 )    

Molecular orbital electronic configuration of H2 =[ s1s ]2  [ s1s* ]0
Bond Order :-1/2[Nb -Na] = 1/2[ 2 -0 ] = 1    
Positive value indicate =stable
It is diamagnetic in nature since the only occupied molecular orbital filled.

Hydrogen molecule ion(H2 +

Total no. of electrons = 1
Molecular orbital electronic configuration of H2 + =[ s1s ]1  [ s1s* ]0
Bond Order :-1/2[Nb -Na] = 1/2[ 1 -0 ] = 1/2
An unpaired electron always indicates that the molecule is paramagnetic.

He2+ molecule ion, 

Total no. of electrons = 3,
Molecular orbital electronic configuration of He2+  cation =[ s1s ]2  [ s1s* ]1
Bond Order :-1/2[Nb -Na] =1/2[ 2 -1 ] = 1/2
Unpaired electron, so paramagnetic.












How do Molecules Bond|Chemical Bond Form

How do Molecules Bond|Chemical Bond Form

How do Molecules Bond

Hello friends, welcome to our blog, today we are going to discuss formation of molecule on the basis of the valence bond theory(VBT).This theory  based on the concept of atomic orbital and also the orbital configuration of atoms.Whenever word chemical bond to hear bond it means tie something together and chemical means that is irreversible by physical means. Lets explain the formation of hydrogen(molecule) as an example. When the hydrogen atom combine to form molecule of hydrogen, energy is released. This shows that the energy of hydrogen molecule is less than as compared to the hydrogen atom.
In general, whenever atom combined to form molecule there is always decrease in the energy which leads to increase the stability. Actually, when atoms of are far separated,they do not have any force of interaction(attraction or repulsion).As they come closest that different forces operate.

1.The nucleus of one atom is attracted towards the electrons of other end and vice versa. Energy is released in a attraction.

2. The nucleus of atom as well as the electrons repel each other.Energy is needed to overcome the force of repulsion.


Formation of hydrogen(H2) molecule


If the magnitude of attractive forces is more than the repulsive forces, then stable molecule will be formed. However if the repulsive forces are more than attractive forces, then the atoms will not combine with each other.

 In the light of above discussion, let us consider the combination between the atoms of hydrogen Ha
and Hb .if Eand Eb are the respective electrons, then the attraction and the force of repulsion may be shown as

Although the number of new attractive and repulsive forces is the same, but the magnitude of attractive forces is more. Thus, when two hydrogen atoms approach each other the overall potential energy of system decreases. Therefore, a stable molecules of hydrogen gets formed.

The potential energy changes which takes place in the formation of hydrogen molecule may be also shown graphically as follow

When the two hydrogen atoms are far separated (at infinite distance) the potential energy is zero. As they start coming closer to each other from infinite distance, energy lost correspondingly. Ultimately, a point of minimum energy is attained when the attractive and repulsive forces are balance each other. At this stage, the hydrogen atoms are bonded together to form a molecule of hydrogen. The distance between the centre of the their nuclear is called bond length.
In case of hydrogen molecule, H-H bond is74 pm. It may be kept in mind start that  two hydrogen atom cannot be brought closer then 74pm.

If it happens then the repulsive forces become more than attractive forces. As a result, potential energy will increase as shown by line. The total decrease in the potential energy when one mole of bond of particular type are formed between the atoms in gaseous state is called bond energy. For example the bond energy of hydrogen hydrogen is 433 kilo joule per mole. It may be noted that the same energy is needed to break the molecules into the atoms is known as bond dissociation energy Thus,bond dissociation energy of hydrogen is also 433 kilo joule per mole.