pH value Formula:
pH is defined as the negative logarithms of H+ ion concentrations here the meaning of the pH is justified as power of hydrogen.
pH= – log10[H+]
In 1909 Sorensen developed a scale (know as pH Scale) on which the strength of acid solutions as well as basic solution could be represented by making use of hydrogen ion concentrations in them.
Formula:
pH= – log10[H+]
- Acidic solution have excess of hydrogen ion [H+] and the basic solution have hydroxide ion [OH-] .
- The pH of solution is inversely proportional to the concentrations of hydrogen ion in it.
- Higher the hydronium ion concentrations present in the solution lower its pH value
- The pH Scale has the value from 0 to 14.
- It scales used for measuring hydrogen ion concentrations.
- For acidic solution pH is <7
- For basic solution pH is >7
- For neutral solution pH = 7
Example :
1) Calculate the pH of 0.1 M of HCl?
pH= – log10[H+]
pH= – log10[0.1] :. – log10= 1
pH = 1
2) Calculate the pH of 10-2 M HCl?
pH= – log10[H+]
pH= – log10[1010-2]
pH = 2
pOH value:
pOH is defined as the negative logarithms of OH- ion concentrations here the meaning of the pOH is justified as power of hydroxide ion.
Formula:
pOH= – log10[OH-]
- POH= exponent of [OH-] ions.
- It is important for measurements of OH- ion concentration or basicity of the solution. Is 1ML-1 of [OH -] ion.
pH + pOH = 14
Example:
Question-1:
Find out the pOH value of a solution having H+ ion concentration of 5×10-4 ?
Solution:.
H+ ion conc.= 5×10-4
pH= – log10[H+]
pH= – log 10-4. – log 5. :. -log5= 0.699
pH=. 4- 0.699
pH = 3.301
So,
pH + pOH = 14
3.301+ pOH =14
pOH = 14 – 3.301
pOH=. 10.699 (basic solution)
Question-2:
Calculate the pH of 0.1 M of NaOH
Solution:
pOH= – log10[OH-]
pOH= – log10[0.1] :. – log10= 1
pOH = 1
So ,
pH + pOH= 14
pH+ 1 = 14
pH = 14 – 1
pH= 13 (because NaOH is base)
Bravo