PH AND CONCENTRATION OF ACID AND BASES

                                 PH AND CONCENTRATION OF ACID AND BASES

PH is a measure of how acidic or basic a solution is.

Solutions with higher concentrations of Hydrogen ions have low PH and are considered acidic. As the concentrations of Hydrogen ions in a solution increase the more acidic the solution becomes since the concentration of H+ is measured in PH units. Therefore this quantifies the amount of [H+] in the form of a positive number.

PH of a solution is the negative log to base 10 of Hydrogen ion concentration (H+) in moles per liter.

                  PH=-log [H+]      (S.P.L  SQ renson (1909)

Solutions with lower concentrations of H+ have higher PHs and are considered as basic. As the level of Hydroxide ions increases the more basic or alkaline the solution becomes. Thus the solution with PH greater than 7 is alkaline. OH- outnumber H+. (Bronsted and Arrhenius 1887)

 

 

 

A solution with PH of 5 has a concentration of 0.00001M

That is;

                  PH=-log [H+]

                     5=-log [H+]

                     Antilog -5=[H+]

                      [H+]=0.00001M

 

A solution with a PH of 6 has a concentration of 0.000001M

That is;

                  PH=-log [H+]

                     6=-log [H+]

                     Antilog -6=[H+]

                      [H+]=0.000001M

Therefore the concentration of PH 5 is higher than that of PH 6

If we compare various household solutions used below we can group them according to their PHs and [H+] Concentrations.

	Most acidic			Least acidic
	Vinegar	Shampoo	Milk	water
PH	3.5	5.5	6.5	7.0
[H+]	10^-3	10^-5	10^-6	10^-7

 

Conjugate acid/base pairs are defined by proton exchange. That is the addition or subtraction of H+. (Ravi Kumar MauryaKSC; 1968)

 

The conjugate acid of water is hydroxonium ion, H3O+. It is formed by the association of H+ with a water molecule.

 

The conjugate acid of Ammonia is Ammonium ion; NH4+

The conjugate acid of SO4- is bisulfate ion; HSO4-

 

SO4- +H+HSO4-

 

 

 

The conjugate base of water is hydroxide ion (OH-)

 

 

 

 

 

The conjugate base of Nitric acid is Nitrate ion (NO3-)

HNO3NO3 _+H+

The conjugate base of Hydrochloric acid is Chloride ion (Cl-)

 

 

 

 

 

 

 

 

 

 

 

 

                                  

 

 

 

 

REFERENCES

 

Atkins and Paula; Physical Chemistry; Acid and base protonations; 9^th edition; 2003 pp789

Bronsted and Arrhenius; Physical Chemistry on PH scale and Concentration of solutions; 5th edition 2001; pp.756

Ravi Kumar MauryaKSC; Conjugate acid and conjugate base definitions and formation; 1968