What concentration of CH3NH3Br is necessary to prepare a pH = 10.00 buffer solution assuming the base concentration is 0.49 M (Kb for CH3NH2 = 4.4 x 10-4). In M
To prepare a buffer solution with a pH of 10.00 using CH3NH3Br and CH3NH2, we can use the Henderson-Hasselbalch equation:
pH = pKa + log ([A-]/[HA])
Here, [A-] represents the concentration of the conjugate base, CH3NH2, and [HA] represents the concentration of CH3NH3Br (the acid component). The pKa value is calculated using the Kb value.
To start, let's find the pKa value:
Kb = [OH-][CH3NH3+]/[CH3NH2]
Kb = [OH-][CH3NH3+]/[CH3NH2]
The concentration of OH- can be calculated from the pH value:
OH- = 10^-(pH)
10^-(pH) = [OH-]
Next, let's substitute the given values into the equation:
4.4 x 10^-4 = [OH-][CH3NH3+]/[CH3NH2]
Since [OH-] is equal to 10^-pH, we can replace [OH-] in the equation:
4.4 x 10^-4 = (10^-pH) [CH3NH3+]/[CH3NH2]
Now, let's rearrange the equation to solve for [CH3NH3+]:
[CH3NH3+] = (4.4 x 10^-4) [CH3NH2] / (10^-pH)
Substituting the given values:
pH = 10.00
[CH3NH2] = 0.49 M
[CH3NH3+] = (4.4 x 10^-4) (0.49 M) / (10^-10)
Calculating the final concentration:
[CH3NH3+] = 2.156 M
Therefore, a concentration of approximately 2.156 M of CH3NH3Br is necessary to prepare a pH = 10.00 buffer solution, assuming the base concentration is 0.49 M.
To determine the concentration of CH3NH3Br necessary to prepare a pH = 10.00 buffer solution, we need to use the Henderson-Hasselbalch equation.
The Henderson-Hasselbalch equation is given by:
pH = pKa + log ([A-]/[HA])
In this case, the base being used is CH3NH2, and its conjugate acid is CH3NH3+. The pKa value can be calculated using the Kb value provided:
Kb = [A-][H+]/[HA]
Since Kb = 4.4 x 10^-4, we can assume [A-] = [H+] and [HA] = [CH3NH2].
Substituting these values into the Kb equation:
4.4 x 10^-4 = [H+]^2 / [CH3NH2]
Since the pH is 10.00, we can calculate [H+] using the formula:
[H+] = 10^(-pH)
[H+] = 10^(-10.00) = 1 x 10^(-10)
Substituting this value of [H+] into the Kb equation:
4.4 x 10^-4 = (1 x 10^(-10))^2 / [CH3NH2]
Simplifying:
4.4 x 10^-4 = 1 x 10^-20 / [CH3NH2]
Cross-multiplying and rearranging:
[CH3NH2] = 1 x 10^-20 / (4.4 x 10^-4)
[CH3NH2] = 2.27 x 10^-17 M
Since [A-] = [H+], the concentration of CH3NH3+ can be taken as the same value.
Therefore, the concentration of CH3NH3Br necessary to prepare a pH = 10.00 buffer solution is 2.27 x 10^-17 M.
pH = pKa + log(base)/(acid)
You have Kb, convert that to pKb, then to pKa by pKa + pKb = pKw = 14.
(CH3NH3B) is the acid.
pH = 10.0
(base) = 0.49M
Solve for (CH3NH3Br)