The concentration of [OH-] in a solution is 1.5 x 10-15 M Which of the following statement is true?

Question

The solution must contain a strong base

The concentration of the acid cannot be determined

The solution is basic

The solution has a high concentration of [H3O+]

The solution has a greater concentration of hydroxide than hydronium

Answer 1

The solution has a high concentration of H₃O⁺

Based on the concentration of OH^- we can find the pOH (pOH= -log₁₀(conc)), this can be used to find pH (pH+pOH=14) and in turn the concentration of H+

You would also find that the pOH is very high (conversely the pH would be very low), indicating that the solution is acidic. This rules out all the other options.

Edited to fix a small formula error

Answer 2

The ionization constant of water is given by:

K_w = 10^-14 = [H₃O⁺][OH^-]

Since we know [OH^-], we can determine [H₃O⁺]:

[H₃O⁺] = (10^-14)/(1.5 x 10^-15 M) = 6.67 M

Based on what we see above, we can conclude that our solution is extremely acidic as [H₃O⁺] is significantly greater than [OH^-]. Therefore:

"The solution has a high concentration of [H₃O⁺]"