Question

How is pH determined? What is the relationship between H+ concentration and pH value?

Answer 1

In order to describe the degree of alkalinity or acidity of a solution we use a unit which is known as pH. pH is basically used to determine concentration of hydrogen ion in a solution and thus give quantitative information of the degree of alkalinity and acidity of solution.

a. pH is determined by the following formula:

pH=-log[H⁺] ----(1)

H⁺ is the concentration of hydrogen ion. By putting the value of H⁺ in the above formula (1) we can determine the pH of any solution.

b. The relationship between pH and H⁺ is:

From the formula given above we can easily determine that the value of pH is directly dependent on the concentration of H⁺. As the ratio of H⁺ changes so does the pH.

For example: When the solution has high concentration of H⁺ then it will result in a low pH

Let's say we have a concentration of H⁺ around 0.1M.

Now put this value in formula (1)

pH=-log[H⁺]

pH= -log[0.1]

pH = 1

When the solution has low concentration of H⁺ then it will have a high pH.

Let's say we have a low concentration of H⁺ around 0.0000001M.

Now put this value in formula (1)

pH=-log[H⁺]

pH= -log[.0000001]

pH = 7