Multiple Choice
What is the pH of a neutral solution at a temperature where Kw = 1.8 × 10^-14?
17. Acid and Base Equilibrium
pH of Strong Acids and Bases
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What volume of 0.855 M KOH solution is required to make 3.55 L of a solution with a pH of 12.4?
A
0.425 L
B
0.500 L
C
0.355 L
D
0.025 L
Verified step by step guidance1
First, understand that the pH of a solution is related to the concentration of hydrogen ions (H⁺) in the solution. A pH of 12.4 indicates a basic solution, so we need to find the concentration of hydroxide ions (OH⁻).
Use the relationship between pH and pOH: \( \text{pH} + \text{pOH} = 14 \). Calculate the pOH by subtracting the given pH from 14: \( \text{pOH} = 14 - 12.4 \).
Convert the pOH to the hydroxide ion concentration \([\text{OH}^-]\) using the formula \([\text{OH}^-] = 10^{-\text{pOH}}\). This will give you the molarity of the OH⁻ ions in the desired solution.
Use the dilution equation \( M_1V_1 = M_2V_2 \), where \( M_1 \) is the initial molarity (0.855 M), \( V_1 \) is the volume of the KOH solution we need to find, \( M_2 \) is the molarity of OH⁻ ions calculated from the pOH, and \( V_2 \) is the final volume of the solution (3.55 L).
Rearrange the dilution equation to solve for \( V_1 \): \( V_1 = \frac{M_2V_2}{M_1} \). Substitute the known values into this equation to find the volume of the 0.855 M KOH solution required.
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