Multiple Choice
What is the pH of a 100.0 mL sample of 0.10 M NH3 before the addition of any HNO3, given that the Kb of NH3 is 1.8 × 10^-5?
17. Acid and Base Equilibrium
pH of Weak Bases
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A solution with a hydroxide ion concentration of 4.15 × 10^-7 M is considered a weak base. What is the hydrogen ion concentration of this solution?
A
2.41 × 10^-8 M
B
4.15 × 10^-7 M
C
2.41 × 10^-7 M
D
1.00 × 10^-7 M
Verified step by step guidance1
Start by understanding the relationship between hydroxide ion concentration \( [OH^-] \) and hydrogen ion concentration \( [H^+] \) in water, which is governed by the water dissociation constant \( K_w \). At 25°C, \( K_w = 1.0 \times 10^{-14} \).
Use the formula \( K_w = [H^+][OH^-] \) to find the hydrogen ion concentration. Rearrange the formula to solve for \( [H^+] \): \( [H^+] = \frac{K_w}{[OH^-]} \).
Substitute the given hydroxide ion concentration \( [OH^-] = 4.15 \times 10^{-7} \) M into the equation: \( [H^+] = \frac{1.0 \times 10^{-14}}{4.15 \times 10^{-7}} \).
Perform the division to calculate \( [H^+] \). This will give you the hydrogen ion concentration in the solution.
Compare the calculated \( [H^+] \) with the provided options to identify the correct answer.
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