What characterizes a base in a solution?

A base in a solution is characterized by its ability to decrease the hydrogen ion concentration. This occurs because bases typically release hydroxide ions (OH⁻) when dissolved in water. The presence of these hydroxide ions reacts with hydrogen ions (H⁺), forming water and thus lowering the overall concentration of hydrogen ions in the solution. This results in an increase in pH, which is a measure of how acidic or basic a solution is.

In contrast to this, substances that increase hydrogen ion concentration are identified as acids, and other components listed do not accurately reflect the defining characteristics of a base. Hence, the correct understanding of a base involves its relationship with hydrogen and hydroxide ions, which is fundamental in acid-base chemistry.