Question

The pH values of five solutions A, B, C, D and E are given below:
A $ 1 $
B $ 5 $
C $ 7 $
D $ 11 $
E $ 13 $
Which solution is:
(A) Weakly Alkaline
(B) Neutral
(C) Strongly Acidic
(D) Strongly Alkaline
(E) Weakly Acidic.

Answer 1

Hint: We know that pH is a measure of how acidic or basic any solution is. The range of pH goes from $ 0 $ to $ 14, $ with $ ~7 $ being neutral i.e. neither acidic nor basic. pH of water can be calculated by measuring the relative amount of free hydrogen and hydroxyl ions in the water.

Complete answer:
As we can see in the question, the pH was tested by a universal indicator. So, before finding the answer, first we have to understand what a universal indicator is and how it works. A universal indicator is an indicator used to measure pH of a solution. It is made up of a solution of several compounds that exhibits several colors which change over a wide range of pH values to indicate the acidity or alkalinity of any given solution. By using a pH paper, we can determine if a particular solution is basic, acidic or neutral. On dipping the paper in the solution, the colour changes, indicating the nature of the solution.
Lesser the pH value more acidic is the solution and higher the pH value more alkaline is the solution.
Weakly alkaline: D $ \left( pH=11 \right) $
Neutral: C $ \left( pH=7 \right) $
Strongly acidic: A $ \left( pH=1 \right) $
Strongly alkaline: E $ \left( pH=13 \right) $
Weakly acidic: B $ \left( pH=5 \right) $ .

Note:
Remember that the pH is defined as the negative logarithm (base $ 10 $ ) of hydrogen ion concentration. It is the most common way to determine the strength of base or acid. Often it is termed as “potential of hydrogen ion”. It is the molarity of $ {{H}^{+}} $ ion.