Question

What does a pH paper indicate of an acidic/alkaline solution?
A) Nature
B) Strength
C) Both A and B
D) None of the above

Answer 1

Chemicals that liberates ${{H}^{+}}$is acidic in nature whereas which liberates $O{{H}^{-}}$ ions are called as basic in nature.
A chemical flavin is present in pH paper.

Complete step by step answer:
The chemicals have their own distinct nature i.e. the chemicals either will be acidic, basic or neutral in nature. The nature of the chemicals is mainly determined by the number of ${{H}^{+}}$ and $O{{H}^{-}}$ions released by a particular chemical in the aqueous solution. And the acidic, basic and neutral of the chemicals is determined using various methods.
First let’s talk about the theory of pH and then will move on the determination of pH using the pH paper.
pH measurement is the most common method to find the strength of the acid or base. pH value is the negative log with base 10 of concentration of Hydrogen ion. pH value is the potential of hydrogen ion or can be said as the molarity of hydrogen ion $\left( {{H}^{+}} \right)$ .
A solution with the pH value equal to 7 is neutral, and a value less than 7 is called acid or acidic in nature and pH values greater than 7 is basic in nature. pH scale ranges from 0-14.
pH scale will only give the nature of the chemical i.e. whether the chemical is neutral, acidic or basic.
As it is a logarithm value, the change in integer number changes the concentration by tenfold.
I.e. pH value 3 is ten times more basic than pH=2.
The pH paper will only give the nature of the chemical. When the pH paper is dipped in a solution, due to a chemical called as flavin present in pH paper which is soluble in water changes the colour of the paper with respect to the solution dipped.
The colour code for the pH paper is,
If the solution is acidic then the paper will turn red, and if it’s basic the paper turns greenish-blue and is light green for neutral solutions.

So the correct answer for the question is option (A).

Note: If we are provided with various solutions we could say the nature of each solution by dipping the pH paper in the solution.
The nature of the chemicals can also be determined using the Universal indicators, which consist of a set of indicators which works on the basis of pH.