Question

What is the nature of the solution at $60^\circ C$ whose pH is 6.35?
A. Acidic
B. Basic
C.neutral
D.none

Answer 1

pH is a figure that is used to express acidity or basicity (Alkalinity) of a solution. pH usually lies in the scale from 0 to 14. When the pH is 7 it is considered neutral. When it is less than 7 it is called Acidic and when it is more than 7 it is called Basic. For example- The human blood is slightly basic with a pH of 7.4.

Complete answer:
The formula of pH is given as-
$pH = - \log \left[ {{H^ + }} \right]$
i.e. pH is the negative logarithm of ${H^ + }$ion concentration.
When we have more Hydrogen ion concentration solution is termed as Acidic.
When we have less hydrogen ion and more hydroxyl ion $(O{H^ - })$ concentration it is basic.
And when both the concentrations are same the solution is considered to be neutral.
pH of the solution is directly dependent on temperature. As the temperature increases molecular vibrations increase and greater dissociation or ionization occurs that produces hydrogen ions and this results in decrease of pH however this temperature effect largely depends on Hydrogen ions and only then the solution becomes acidic in nature. Therefore all the pH measurements are performed at the same temperature to prevent any error.
In the given question we are given the pH of 6.35 at a temperature of 60 °C which is less than 7 but almost close to 7 so we can say that the solution is slightly acidic in nature and the option closest to our observation is option (A).
And hence the correct answer is option A.

Note:
The word pH is short for ‘pondus Hydrogenium’. We perform several experiments in the laboratory and our teachers advise us to maintain a proper temperature of the solution and proper pH. For example in chlorination reaction pH is important to be maintained. Also Enzyme activity largely is affected by pH since these are proteins and hence denature at high pH values.