Use the relationship between pH and [H+]. The square brackets denote concentration (molarity).
pH = - log[H+]
pOH = - log[OH-]
pH + pOH = 14
a. If you have an acidic solution with a pH of 4.6, what is the concentration of H+ (or [H+])?
b. For the solution in (a) what is the concentration of OH-?
c. If you have a solution with a [H+] = 0.01546 M, what is the pH of the solution?
d. For the solution in (c), what is the [OH-]?