Multiple Choice
Which of the following correctly completes the autoionization reaction of water and provides the expressions for its equilibrium constant (K_c) and ion product (K_w)?
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17. Acid and Base Equilibrium
Auto-Ionization
Multiple Choice
Chemistry student prepared an aqueous solution at 30ºC. If the solutions contains 7.42 × 10−9 M of hydroxide ions, calculate the pH.
A
5.703
B
8.130
C
8.300
D
5.980
Verified step by step guidance1
Start by understanding the relationship between hydroxide ions (OH⁻) and hydrogen ions (H⁺) in water. The product of their concentrations is constant at a given temperature, known as the ion product of water (Kw). At 30ºC, Kw is approximately 1.47 × 10⁻¹⁴.
Use the formula Kw = [H⁺][OH⁻] to find the concentration of hydrogen ions. Rearrange the formula to solve for [H⁺]: [H⁺] = Kw / [OH⁻].
Substitute the given concentration of hydroxide ions (7.42 × 10⁻⁹ M) and the value of Kw (1.47 × 10⁻¹⁴) into the equation to calculate [H⁺].
Once you have the concentration of hydrogen ions, use the formula for pH: pH = -log₁₀[H⁺].
Calculate the pH using the hydrogen ion concentration obtained in the previous step. This will give you the pH of the solution.
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