If the pH of a solution changes from 6 to 4, how does its acidity change?

When the pH of a solution changes, it indicates a change in the hydrogen ion concentration in that solution. The pH scale is logarithmic, meaning that each whole number change on the scale represents a tenfold change in acidity.

In this case, the pH changes from 6 to 4. To understand the increase in acidity, we can calculate how many whole number steps have been made on the pH scale: from 6 down to 5 is one step, from 5 down to 4 is another step. That’s a total of two steps.

Since each step represents a tenfold increase in hydrogen ion concentration, the increase in acidity from a pH of 6 to a pH of 4 is calculated as follows:

• From pH 6 to pH 5: 10 times more acidic.
• From pH 5 to pH 4: another 10 times more acidic.

Therefore, the total change in acidity is 10 times 10, which equals 100 times. This means that when the pH of a solution changes from 6 to 4, it becomes 100 times as acidic.