Question
Question: Calculate the hydronium ion \[[{H_3}{O^ + }]\] and hydroxide ion \[[O{H^-}]\] concentration for a \(...
Calculate the hydronium ion [H3O+] and hydroxide ion [OH−] concentration for a 0.0368MNaOH
Solution
To answer this question, you should recall the concept of pH scale. The pH scale is a logarithmic scale that is used to measure the acidity or the basicity of a substance. The possible values on the pH scale range from 0 to 14.
The formula used: pOH = −log[OH−] and pH+pOH=14
Complete Step by step solution:
The term pH is an abbreviation of potential for hydrogen. Acidic substances have pH values ranging from 1 to 7 and alkaline or basic substances have pH values ranging from 7 to 14. A perfectly neutral substance would have a pH of exactly 7.
The pH of a substance can be expressed as the negative logarithm of the hydrogen ion concentration in that substance. Similarly, the pOH of a substance is the negative logarithm of the hydroxide ion concentration in the substance. These quantities can be expressed via the following formulae:
pH = −log[H+] and pOH = −log[OH−].
The given 0.0368MNaOH will dissociate to give 0.0368moles of hydroxide ions.
[OH−]=0.0368M
This concentration of hydroxide ions can be used to calculate the pOH of solution:
pOH = −log[0.0368]=1.4341.
From this, we can calculate the pH using:
pH+pOH=14.
The value of pH will be pH=12.565.
Now pH = −log[H+] can be used to calculate the hydronium concentration:
[H3O+]=2.71×10−13.
Note: You should know about the limitations of pH Scale
pH values do not reflect directly the relative strength of acid or bases: A solution of pH = 1 has a hydrogen ion concentration 100 times that of a solution of pH = 3 (not three times).
pH value is zero for 1 N the solution of the strong acid. The concentration of 2 N, 3 N, 10 N, etc. gives negative pH values.
A solution of an acid having very low concentration, say 10 - 8N shows a pH = 8and hence should be basic, but actual pH value is less than 7.