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Question: How do you calculate \[pOH\]of \(NaOH\) ?...

How do you calculate pOHpOHof NaOHNaOH ?

Explanation

Solution

The aqueous solution of acids, base and neutral solution consists of H+{{H}^{+}} and OH−O{{H}^{-}} ions. Sodium hydroxide is a strong base which when dissolved in water, it forms a sodium hydroxide solution. The water dissociates to give H+{{H}^{+}} and OH−O{{H}^{-}} ions.

Complete step-by-step answer: pOHpOH is used to calculate the number of hydroxide ions in the solution. It basically tells us the alkalinity of the solution. It is calculated by the negative logarithm of hydroxide ion concentration.
Let us see the formula –
pOH=−log⁡[OH−]pOH=-\log \left[ O{{H}^{-}} \right]
Where, [OH−]\left[ O{{H}^{-}} \right] is the concentration of hydroxide ion
A basic solution has pOHpOH value less than 77 .
You can calculate the pOHpOH if you know the sodium hydroxide concentration. You should know the molarity of NaOHNaOH
Lets us discuss with an help of an example-
Calculate the pOHpOH of 10−7M{{10}^{-7}}M NaOHNaOH solution
As we know that sodium hydroxide is a strong base, it will completely dissociate to give hydroxide ions.
We will add the contribution of water, because it is an aqueous solution of sodium hydroxide.
⇒[OH−]=10−7+10−7\Rightarrow \left[ O{{H}^{-}} \right]={{10}^{-7}}+{{10}^{-7}}
⇒[OH−]=2×10−7\Rightarrow \left[ O{{H}^{-}} \right]=2\times {{10}^{-7}}
To find the concentration hydroxide ions, we use pOHpOH formula,
pOH=−log⁡[OH−]pOH=-\log \left[ O{{H}^{-}} \right]
⇒pOH=−log⁡[2×10−7]\Rightarrow pOH=-\log \left[ 2\times {{10}^{-7}} \right]
⇒pOH=7−log⁡2\Rightarrow pOH=7-\log 2
⇒pOH=7−0.3\Rightarrow pOH=7-0.3
⇒pOH=6.7\Rightarrow pOH=6.7
This is how you can calculate the pOHpOH of sodium hydroxide solution.

Note: In this question, we have calculated the value of pOHpOH using concentration of hydroxide ions.
Kb{{K}_{b}} is defined as the dissociation constant of a base. If the value of dissociation constant of a base is high then it is a strong base whereas if the value of dissociation constant of a base is low then it is a weak base.
Ionization is a process in which a neutral molecule breaks down and splits into charged ions in aqueous solution. According to Arrhenius theory, bases dissociate to give hydroxide ions.