Calculate [OH-] in each aqueous solution at 25 °C, and classify the solution as acidic or basic. a. [H3O+] = 1.2 * 10^-8 M b. [H3O+] = 8.5 * 10^-5 M c. [H3O+] = 3.5 * 10^-2 M

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Identify the relationship between [H3O+] and [OH-] using the water dissociation constant (Kw) at 25 °C, which is 1.0 x 10^-14. The formula is: [H3O+][OH-] = Kw.

For each part (a, b, c), rearrange the formula to solve for [OH-]: [OH-] = Kw / [H3O+].

Substitute the given [H3O+] values into the formula to calculate [OH-] for each solution.

Compare the calculated [OH-] with [H3O+] to determine if the solution is acidic or basic. If [H3O+] > [OH-], the solution is acidic. If [OH-] > [H3O+], the solution is basic.

Classify each solution based on the comparison: a. If [OH-] > 1.2 x 10^-8 M, it's basic. b. If [OH-] < 8.5 x 10^-5 M, it's acidic. c. If [OH-] < 3.5 x 10^-2 M, it's acidic.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

pH and pOH

pH is a measure of the hydrogen ion concentration in a solution, defined as pH = -log[H3O+]. pOH, on the other hand, measures the hydroxide ion concentration, calculated as pOH = -log[OH-]. At 25 °C, the relationship between pH and pOH is given by the equation pH + pOH = 14, which helps classify solutions as acidic (pH < 7) or basic (pH > 7).

Ion Product of Water (Kw)

The ion product of water, Kw, is the equilibrium constant for the self-ionization of water, defined as Kw = [H3O+][OH-]. At 25 °C, Kw is equal to 1.0 x 10^-14. This relationship allows us to calculate the hydroxide ion concentration [OH-] from the hydronium ion concentration [H3O+] using the formula [OH-] = Kw / [H3O+].

Acidic and Basic Solutions

A solution is classified as acidic if it has a higher concentration of hydronium ions [H3O+] than hydroxide ions [OH-], resulting in a pH less than 7. Conversely, a basic solution has a higher concentration of hydroxide ions, leading to a pH greater than 7. Neutral solutions have equal concentrations of both ions, typically at pH 7. Understanding these classifications is essential for interpreting the results of the calculations.