Question

In a water treatment plant, the ph values of incoming & outgoing water are 7.2 & 8.4 respectively. Assuming a linear variation of ph with time, determine the average ph value of water.

Answer 1

The average ph value of water is -7.22 + Log_10 (Vt / V2)

Concentration in the incoming water = 7.2 (Given)

Concentration in the outgoing water = 8.4 (Given)

Therefore,

Number of ions that came in t hours  = 10`{-7.2} Vt

Number of ions that went out in t hours = 10`{-8.4} Vt

Concentration of ions in the container at t hours will be -

10`-7.2 - 10`-8.4 ) Vt = Vt × [ (10^1.2 - 1) ] × 10^-8.4   

Average number of ions in moles per litre at t hours will be -  

= Vt × (10^1.2 - 1)  × 10^-8.4 / V2

( H+) = (10^1.2 - 1) ] × 10^-8.4 × (Vt / V2)

Taking log values -

pH  = -7.22 + Log_10 (Vt / V2)