pH level of water

What is pH level of water?

The term pH means “Power of Hydrogen” or “Potential of Hydrogen” in chemistry. But simply pH level of water indicates the concentration of hydrogen ion in water.

pH Formula & pH Scale:

pH = -log[H+]

Based on hydrogen ion concentration pH scale is developed. pH scale ranges from 0 to 14. pH value 7 is considered as neutral water.

Water having a pH value between 0 to less than 7 is considered as a acidic water & from greater than 7 to 14 considered as basic or alkaline water.

pH scale of water
pHNature of Water
< 7.0Acidic
> 7.0Basic OR Alkaline
pH Table

pH Test:

It is accurately determined by pH Meter. However you can also check approximate pH value by pH indicator or pH test strips.

Nowadays, It’s very easy to test pH of water. All you need to do is simply purchase the pen type pH meter & dip it into the water sample.Display shows the pH of sample.

 pH Calculation:

Let’s take example & Calculate pH:

How to calculate the pH & hydrogen ion concentration of 0.1M Hydrochloric Acid?

Hydrochloric Acid(HCl) is strong acid. It is fully dissociate into H+ and Cl- ions.

Formula to calculate pH:

pH = -log[H+]

[H+] indicates the concentration. In our example it is 0.1M

pH = -log[0.1] =1

So, The pH of 0.1M Hydrochloric Acid is 1.

Formula to calculate Hydrogen ion(H+) concentration

H+ = 10 ^ -pH

H+ = 10 ^ (-0.1) = 0.1M

This is reverse calculation of pH.

Let’s take another example & Calculate pH of Weak Acid:

How to calculate pH of 0.7M Acetic Acid? Ka value of acetic acid is 1.8 × 10^(-5)

Dissociation of acetic acid,


Ka = [H+][CH3COO-] ÷ [CH3COOH]

put values in formula,

1.8 × 10^(-5) = [x] × [x] ÷ [0.7]

X2 = 1.8 × 10^(-5) × 0.7

X = √[0.7 × 0.00018] = 0.0112

0.0112 is the concentration of H+ ion in 0.7M acetic acid solution.

put this value in pH formula,

pH = -log[0.0112] = 1.95

So, The pH of 0.7M acetic acid is 1.95

In summary, pH level of water indicates the nature of water. Water having a very low or very high pH is a sign of contaminant present in water.

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