An unknown weak base with a concentration of 0.170 M has a pH of 9.37. What is the Kb of this base?
Question
An unknown weak base with a concentration of 0.170 M has a pH of 9.37. What is the K<sub>b</sub> of this base?
Solution
To solve this problem, we need to use the formula for pH and the formula for Kb (the base ionization constant).
Step 1: Calculate the concentration of OH- ions The pH of a solution is related to the pOH by the equation: pH + pOH = 14.00 So, we can find the pOH of the solution: pOH = 14.00 - pH = 14.00 - 9.37 = 4.63
The pOH is related to the concentration of OH- ions by the equation: pOH = -log[OH-] So, we can find the concentration of OH- ions: [OH-] = 10^-pOH = 10^-4.63 = 2.34 x 10^-5 M
Step 2: Calculate the concentration of the base The concentration of the base is given as 0.170 M.
Step 3: Calculate the Kb of the base The Kb is related to the concentrations of the base and the OH- ions by the equation: Kb = [OH-]^2 / [Base] So, we can find the Kb of the base: Kb = (2.34 x 10^-5)^2 / 0.170 = 3.23 x 10^-10
So, the Kb of the base is 3.23 x 10^-10.
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