What is the Henderson-Hasselbach equation? Use the equation to determine the ratio of [A-] to [HA] necessary to create an ammonium chloride/ammonia buffer with a pH of 8.50. Describe how to make this buffer given a solution of 0.1 M NH3 (aq) and a bottle of NH4Cl(s).
pH = pKa + log(base)/(acid)
Plug in pH you want, plug in pKa for NH3 (that will be Kw/Kb since you can't find the Ka listed in any table), you're given NH3 (make up a volume for that and enter moles), solve for (NH4Cl). Convert to grams in the volume you chose for the NH3.
how many milliliters of 0.500 M NaOh should be added to 10.0 grams of tris hydro-chloride to give a pH of 7.60 in a final volume of 250 mL
The Henderson-Hasselbach equation is a mathematical expression used to calculate the pH of a solution containing a weak acid and its conjugate base or a weak base and its conjugate acid. It is given by the equation:
pH = pKa + log([A-]/[HA])
where pH is the desired pH of the buffer solution, pKa is the negative logarithm of the acid dissociation constant, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the weak acid.
To determine the ratio of [A-] to [HA] necessary to create an ammonium chloride/ammonia buffer with a pH of 8.50, we need to rearrange the Henderson-Hasselbach equation as follows:
pH - pKa = log([A-]/[HA])
10^(pH - pKa) = [A-]/[HA]
[A-]/[HA] = 10^(pH - pKa)
Given that the pH is 8.50, we need to know the pKa value for the ammonium-ion (NH4+) to find the ratio of [A-] to [HA].
To make the ammonium chloride/ammonia buffer, with the solution of 0.1 M NH3 (aq) and the bottle of NH4Cl(s), follow these steps:
1. Calculate the pKa value for the ammonium-ion (NH4+) by looking it up in a reliable reference source or finding literature values. Let's assume the pKa value for NH4+ is approximately 9.25.
2. Substitute the values into the Henderson-Hasselbach equation. Using the equation [A-]/[HA] = 10^(pH - pKa), we have:
[A-]/[HA] = 10^(8.50 - 9.25)
[A-]/[HA] = 10^(-0.75)
[A-]/[HA] ≈ 0.177
This means that to create the buffer solution with a pH of 8.50, the ratio of [A-] (NH3) to [HA] (NH4Cl) should be approximately 0.177.
3. To make the buffer solution, start by dissolving the NH4Cl(s) in a known volume of water to create a specified concentration, such as 0.1 M NH4Cl. Make sure the solution is thoroughly mixed.
4. Add the 0.1 M NH3(aq) solution to the NH4Cl solution and adjust the volume to obtain the desired concentration of both NH3 and NH4+ according to the calculated ratio. For example, if you want to make a 1-liter buffer solution, add 0.177 liters (or 177 mL) of the 0.1 M NH3(aq) solution to 0.823 liters (or 823 mL) of the 0.1 M NH4Cl solution.
5. After mixing, ensure that the pH of the buffer solution is 8.50. Adjust the pH, if needed, using a pH meter and an appropriate acid or base solution, such as sodium hydroxide (NaOH) or hydrochloric acid (HCl).
Remember to use appropriate safety precautions, follow proper laboratory procedures, and double-check all calculations and measurements when preparing buffer solutions.