Question

question
roughly how many water molecules are ionized at any given time in a sample of room - temperature water?
select the correct answer below:
one in a thousand
one in a million
one in a billion
one in a trillion

Explanation:

At room temperature, water undergoes a slight ionization. The ionization constant of water \(K_w = [H^+][OH^-]=1\times10^{- 14}\) (at \(25^{\circ}C\)). The concentration of water is approximately \(55.5\space mol/L\). The ratio of ionized water molecules to total water molecules can be calculated. The concentration of \(H^+\) (or \(OH^-\)) from water ionization is \(1\times10^{-7}\space mol/L\). The ratio \(\frac{1\times 10^{-7}}{55.5}\approx1.8\times10^{-9}\), which is roughly one in a billion.

Answer:

one in a billion