short note on pH scale

Dear students,
pH Scale :
The concept of p[H] was first introduced by Soren Peder Laurotz Sorensen at the Carlsberg Laboratory  in 1909 and revised to the modern pH in 1924 to accommodate definitions and measurements in terms of electrochemical cells. 

The exact meaning of the "p" in "pH" is disputed, but according to the Carlsberg Foundation pH stands for "Power of hydrogen". It has also been suggested that the "p" stands for the Potenz (meaning "power"), others refer to "potential" or potential hydrogen.

The pH scale is a universal acid -base indicator which changes its color depending upon the strength of the acid or base solutions. It consists of several divisions and the value ranges from 0 to 14, which indicates the concentration of H+ ion or [H3O]+ ion or hydroxide ion [OH]- ion. 

In the pH scale, 7 is considered as the neutral point and below seven show acidity and above 7 shows basicity.

The change in color of the scale depends on the value of pH of the solution and it ranges as:

pH = 0 dark red , 1= red ,2= orangey red ,3= orange, 4 =yellowy orange, 5= yellow, 6= greeny yellow, 7= green, 8 = greeny blue, 9 =dark greeny blue, 10= blue, 11= dark blue, 12=  purpley blue, 13=  purple, 14= dark purple.

The circular representation is :


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