PH

  PH  Defination, Calculation, Limitation 

In this blog how to learn P^H Defination calculation limitation. Soren Peter Lauritz Sorensen was denish  chemist known for the introduction of the concept of  P^H  scale measure acidity and basicity.

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What   is  full form P^H ? 

P^H  full form is potential of hydrogen.
P^H  defined as the negative logarithm of  H⁺ ion  and  H₃O⁺ concentration.
P^H  scale is  measuring Acid and Bases.

What is a P^H  scale ?

P^H  scale range is 0 – 14
Acidic PH  = 0 – 7
neutral PH  = 7
Alkaline PH = 7 – 14

Example

NO.	Materials	PH Value
01	Battery Acid	0
02	HCL	1
03	Lemon Juice	2
04	Vinegar	3
05	Orange Juice	3.5
06	Coffee	5
07	Pure Water	7
08	Human Blood	7.35
09	Milk	6.5-6.7
10	Backing Soda	8.5-9.0
11	Ammonia Solution	11
12	Bleaching liquid	12.6
13	Oven Cleaner	13
14	NaOH	14

P^H Formula

P^H = -log [H⁺]
P^H  = -log [H₃O⁺]
P^OH = -log [OH^–] 
Distilled waterH₃O⁺= OH^– =  10 ^-7  at  298 K.
If concentration of H₃O⁺   is more than 10 ^-7  then solution becomes Acidic.
If   concentration of  OH^–   is more than  10 ^-7  then solution becomes Basic.
Distilled water concentration of  H₃O⁺ and OH^–  is a same so it is neutral.

Why P^H value is 0 to 14 ?

H₃O⁺= OH^– =  10 ^-7
=H₃O⁺ × OH^–
= 10 ^-7 × 10 ^-7
= -log₁₀ [H₃O⁺] + -log₁₀ [OH^–] 
= -log₁₀ [ 10 ^-7] + -log₁₀ [ 10 ^-7] 
= -log₁₀ 10 ^-14
= 14 Log₁₀ ¹⁰ p[OH^–] + p[H₃O⁺]
= 14

P^{H measuring   3 way}

^{01.) Litmus test}

P^H Measuring through litmus paper :

^{Basic :
RED  ——-    BLUE}

^{Acidic:
BLUE  ——-   RED}

^{02.) universal indicator} 

Universal indicator is dropwise feed in solution then colour change according  P^H.
Acidic colour red to pink.
Basic color gives to blue.

03.)P^{H meter} 

P^H  meter electrode use potassium chloride solution based KCL is P^H  neutral.
P^H  meter is device by we can check accurate P^H  of solution.

How to calculate P^H  ?

01.) Define  0.01 M  HCL    P^H ? 

HCL ——   H⁺     +   Cl^–

^Initial

0.01         0.0        0.0

Final

0.0         0.01      0.01

= 10 ^-2

P^H = -log [H⁺]

P^H = -log 10 ^-2

P^H = 2 log 10

P^H =2

02.) Define 0.005 M H₂SO₄  P^H ?

H₂SO₄ —–  2H⁺    +   SO₄^-2

0.005            0.0           0.0

0.0                    0.005          0.005

0.0          0.005 × 2 Mole   0.005

0.0                   0.01               0.005

= 10 ^-2

P^H = -log [H⁺]

P^H = -log 10 ^-2

P^H = 2 log 10

P^H =2

03.) Define 0.01M NaOH P^H ?

NaOH ——   Na⁺   +  OH^–

0.01                     0.0             0.0

0.0                      0.01            0.01

= 10 ^-2

P^OH = -log [OH^–] 

P^OH = -log 10 ^-2

P^OH = 2 log 10

P^{OH =  2}

P^{H   +}  P^OH = 14

P^{H = 14-    2}

  P^{H  = 14 – 2}

P^{H = 12}

Why doesn’t solvent  have a P^H  ? 

Most organic solvent do not have ionizable H⁺ ions so they won’t give a proper reading in a   P^H  meter.

P^H   Scale Limitation ?

P^H scale on for Aqueous solution.
P^H applicable for concentration H₃O⁺  ions is less than 1M.
P^H limit is 0 – 14.