Find [OH^-] and the pH of the following solutions. (a) 0.25 g barium hydroxide, Ba(OH)2, dissol

step 1 Looking at the first part of this question, we have to recall that the molarity M is equal to th

Find [OH^-] and the pH of the following solutions. (a) 0.25...

Find $\left[\mathrm{OH}^{-}\right]$ and the $\mathrm{pH}$ of the following solutions. (a) $0.25 \mathrm{~g}$ barium hydroxide, $\mathrm{Ba}(\mathrm{OH})_{2},$ dissolved in enough water to make $0.655 \mathrm{~L}$ of solution (b) A $3.00 \mathrm{~L}$ solution of $\mathrm{KOH}$ is prepared by diluting $300.0 \mathrm{~mL} 0.149 \mathrm{M} \mathrm{KOH}$ with water.

Find $\left[\mathrm{OH}^{-}\right]$ and the $\mathrm{pH}$ of the following solutions.
(a) $0.25 \mathrm{~g}$ barium hydroxide, $\mathrm{Ba}(\mathrm{OH})_{2},$ dissolved in enough water to make $0.655 \mathrm{~L}$ of solution
(b) A $3.00 \mathrm{~L}$ solution of $\mathrm{KOH}$ is prepared by diluting $300.0 \mathrm{~mL} 0.149 \mathrm{M} \mathrm{KOH}$ with water.

Key Concepts

pH and pOH Relationship

The pH and pOH of a solution are measures of its acidity and basicity, respectively, and are related by the equation pH + pOH = 14 (at standard temperature). For solutions involving strong bases, the hydroxide ion concentration is used to calculate pOH, which, in turn, is used to determine the pH. This relationship is vital for understanding the overall properties of the solution.

Molarity and Concentration Calculations

Molarity is the measure of the concentration of a solute in a solution, defined as the number of moles of solute per liter of solution. Understanding how to calculate molarity from a given mass of substance or from a prepared solution is crucial when determining the concentrations of chemical species in a solution.

Stoichiometry of Strong Base Dissociation

Strong bases, such as barium hydroxide and potassium hydroxide, dissociate completely in water. The stoichiometry of the dissociation reaction indicates how many hydroxide ions (OH–) are produced per formula unit of the strong base. This concept is fundamental in calculating the total hydroxide ion concentration in a solution based on the original concentration of the base.

Dilution Principle

The dilution principle involves calculating the new concentration of a solution after it has been diluted with additional solvent. The key relationship used is that the product of the initial concentration and the initial volume equals the product of the final concentration and the final volume. This concept is essential in preparing solutions of a desired molarity from a more concentrated stock solution.

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