What does a decrease in pH from 3 to 2 represent in terms of hydrogen ions?

A decrease in pH from 3 to 2 indicates an increase in hydrogen ion concentration. The pH scale is logarithmic, which means that each whole number change on the scale represents a tenfold change in the concentration of hydrogen ions.

When the pH value decreases from 3 to 2, it reflects a transition from a less acidic environment (with a pH of 3) to a much more acidic environment (with a pH of 2). Specifically, a pH of 3 corresponds to a hydrogen ion concentration of 0.001 mol/L (or 10^(-3) mol/L), and a pH of 2 corresponds to a hydrogen ion concentration of 0.01 mol/L (or 10^(-2) mol/L). This means that when the pH drops by 1 unit, the hydrogen ion concentration increases tenfold, hence confirming that a decrease from pH 3 to pH 2 represents a tenfold increase in hydrogen ion concentration.