A sample of orange juice is found to have a pH of 3.80. What is he concentration of the hydroxide ion in the juice?

To find the concentration of hydroxide ion in the orange juice, we need to use the equation for the ionization constant of water (Kw), which is Kw = [H+][OH-] = 1.0 x 10^-14 at 25°C. Since we know the pH of the orange juice is 3.80, we can find the concentration of hydrogen ions [H+] using the equation pH = -log[H+]. So, pH 3.80 is equivalent to [H+] = 1.58 x 10^-4 M. To find the concentration of hydroxide ions [OH-], we can rearrange the equation for Kw to get [OH-] = Kw/[H+]. Substituting the values we found, we get [OH-] = 6.3 x 10^-11 M. Therefore, the correct option is 6.3 x 10^-11.