Question

How do you calculate the pH of $0.075M$ $KOH$?

Answer 1

Hint: pH denotes the power of hydrogen or we can say that it represents potential of hydrogen ions. It is generally a scale which is used to represent that aqueous solution given is acidic in nature, basic in nature or in neutral form.

Complete answer:
pH scale is said to be logarithmic because it inversely indicates the concentration of hydrogen ions in the solution. Formula used to calculate pH approximately equal to the negative of the base 10 logarithmic of the molar concentration which can be represented as follows:
$pH=-{{\log }_{10}}[{{H}^{+}}]$
$KOH$ is basic in nature, base are those substances which have hydroxide ions in them and we can see that $KOH$ is composed of ${{K}^{+}}$and $O{{H}^{-}}$ ions. pH can also be explained on the basis of basicity i.e. with the help of hydroxide ions it also gives the same formula which is represented by
$pH=-{{\log }_{10}}[O{{H}^{-}}]$
Therefore, the pH of $KOH$ is calculated with the help of formula
$pH=-{{\log }_{10}}[O{{H}^{-}}]$i.e. $pOH=-{{\log }_{10}}[0.075]$
$pOH=-(-1.12)=+1.12$
We know that under standard conditions in aqueous solutions $pH+pOH=14$
Therefore, from this concept we can find the value of pH by subtracting the value of pOH from 14 i.e. $pH=14-1.12=12.88$
Hence, the pH of $0.075 M$ solution of $KOH$ is 12.88.

Note: pH scale ranges from 0-14 where the solution which has the value greater than 7 is basic in nature and those solutions who have value less than 7 are acidic in nature and those who have exact 7 value are said to be neutral in nature.