Calculate the pH when 25.0ml of 0.90M CH3COOH is mixed with 25.0ml of 0.45M NaOH.

pH of mixed solution = 4.3

A buffer solution is a solution that can maintain a good pH value due to the addition of a little acid or a little base or dilution.  

The buffer solution can be acidic or basic  

Acid buffer solution consists of weak acids and their salts.  

valence according to the amount of salt anion  

mol CH₃COOH = 25 ml x 0.9 = 22.5 mlmol

mol NaOH = 25 ml x 0.45 = 11.25 mlmol

ICE method :

Reaction

NaOH + CH₃COOH ---> CH₃COONa + H₂O

11.25       22.5

11.25       11.25                       11.25        11.25

               11.25                        11.25        11.25

mol acid = 11.25, mol salt = 11.25, Ka CH₃COOH = 5.10⁻⁵

Then [H⁺]=

the electronic configuration of an atom with eight electrons is 1s²2s²2p⁴. the orbital diagrams are shown in the figure.

as per the hunds rule:

1. electrons tend to avoid being in the same orbital as per as practicable.

2. electrons in different orbitals of the same energy will have their spin parallel.

this can be illustrated from the multiplicity of the orbitals of the atom. as there are four electrons in the p orbital and p orbital has 3 sub-shells. the electrons can be fed in different ways as shown in the figure but the correct orbital diagram will be as per the hunds rule.

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