Solveeit Logo
Login

Question

Question: If \([OH^-]= 5.0 × 10^{-5}\) M then pH will be: A. \[5-\log 5\] B. \[9+\log 5\] C. \[\log 5-5\...

If [OH−]=5.0×10−5[OH^-]= 5.0 × 10^{-5} M then pH will be:
A. 5−log⁡55-\log 5
B. 9+log⁡59+\log 5
C. log⁡5−5\log 5-5
D. log⁡5−9\log 5-9

Explanation

Solution

The pH of a solution is negative-logarithm of hydrogen ion concentration. As with the hydrogen-ion concentration, the concentration of the hydroxide ion can be expressed logarithmically by the pOH. The pOH of a solution is the negative-logarithm of hydroxide-ion concentration in that solution. Regardless of what is added to the solution the sum of pH and pOH will be always 1.0 x 10−1410^{-14} at 25oC25^oC.
⇒pH+pOH=14\Rightarrow {{p}{H}}+{{p}{OH}}=14

Complete step by step answer:
Given that,[OH-]= 5.0 × 10-5, hence the pOH will be,
⇒pOH=−log⁡[OH−]\Rightarrow {{p}{OH}}=-\log [O{{H}^{-}}]
=−log⁡(5×10−5)=-\log (5\times {{10}^{-5}})
pOH=5−log⁡5{{p}{OH}}=5-\log 5
Now, we have known that,
⇒pH+pOH=14\Rightarrow {{p}{H}}+{{p}{OH}}=14
⇒pH=14−pOH\Rightarrow {{p}{H}}=14-{{p}{OH}}

   $$\Rightarrow {{p}{H}}=9+\log 5$$

Hence, the correct option is B.

Note:
pH is a measure of how acidic/basic water is. The range goes from 0 to 14, with 7 being neutral. When pH of less than 7 indicates acidity, whereas a pH of greater than 7 indicates a base.The pH and pOH are really a measure of the relative amount of free hydrogen and hydroxyl ions in the water.