The pH Scale is a set of numbers from 0 to 14 which is used to indicate whether an aqueous solution is acidic, neutral or alkaline.
All aqueous solutions contain hydrogen ions, H+ and hydroxide ion, OH–. The concentration of these ions differs in solutions of different pH values. Therefore, the pH of a solution is related to the concentration of hydrogen ions or hydroxide ions present in a solution.
It is important to appreciate the formal definition of “pH” in order to master Chemistry. It is formally defined as the “measure of the concentration of the hydrogen ions in a solution”.
Based on the definition above, let’s look at three different sections of the pH Scale:
A) Solution with pH equal to 7
It is NEUTRAL!
This if the pH of pure water i.e. distilled water.
The concentration of hydrogen ions and hydroxide ions is the same.
B) Solution with pH less than 7
It is ACIDIC!
Acids have concentration of hydrogen ions more than the concentration of hydroxide ions.
The lower the pH value, the greater the concentration of hydrogen ions and the lower the concentration of hydroxide ions, which means the more acidic the solution.
C) Solution with pH greater than 7
It is ALKALINE!
Acids have concentration of hydroxide ions more than the concentration of hydrogen ions.
The higher the pH value, the greater the concentration of hydroxide ions and the lower the concentration of hydrogen ions, which means the more alkaline the solution.
Let’s take a look at a Chemistry MCQ question.
Question 1:
An unknown aqueous solution has a pH value of about 2.
Which of the following is correct about the ions present in the solution?
A) Concentration of H+ ions = High & Concentration of OH– ions = None
B) Concentration of H+ ions = High & Concentration of OH– ions = Low
C) Concentration of H+ ions = Low & Concentration of OH– ions = High
D) Concentration of H+ ions = Low & Concentration of OH– ions = None
Work on it and write your answer in the comment section below. See you soon!
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