# What is the molar concentration of hydronium ion in pure water at 25 degrees C?

${10}^{-} 7$ $m o l \cdot {L}^{-} 1$.
${K}_{\text{water}}$ $=$ $\left[{H}_{3} {O}^{+}\right] \times \left[H {O}^{-}\right] = {10}^{-} 14$ at $298 \cdot K$
At temperatures above $298 \cdot K$, how do you think this equilibrium would evolve?