What is the equilibrium constant (K) value at neutral pH?

At neutral pH, the concentration of hydrogen ions ([H^+]) in pure water is (1 \times 10^{-7}) M. The equilibrium expression for the self-ionization of water can be represented as:

[ H_2O \rightleftharpoons H^+ + OH^- ]

The equilibrium constant (K_w) for this reaction (which also reflects the product of the concentrations of hydrogen and hydroxide ions) can be expressed as:

[ K_w = [H^+][OH^-] ]

At 25°C, the concentrations of (H^+) and (OH^-) at neutral pH are equal, both being (1 \times 10^{-7}) M. Therefore, we can substitute these values into the equilibrium expression:

[ K_w = (1 \times 10^{-7})(1 \times 10^{-7}) = 1 \times 10^{-14} ]

The value (K_w) is temperature-dependent, and at 25°C it is (1 \times 10^{-14}). Thus, at neutral pH, where the pH is defined as 7, the equilibrium constant