Question

Which of the following buffer systems would be the best choice to create a buffer with pH 9.10?
a) HF/KF (pKa = 3.14)
HNO2/KNO2 (pKa = 3.39)
NH3/NH4Cl (pKa = 9.25)
HClO/KClO (pKa = 7.46)
b) for the best buffer system, calculate the ratio of the molarities of the buffer components required to make the buffer
c) for the best buffer system, calculate the ratio of the masses of the buffer components required to make 1.00 L of the buffer

Answer 1

Answer:

a) NH3/NH4Cl (pKa = 9.25)

b) $\frac{[Base]}{[Acid]} =0.708$

c)

Explanation:

Hello,

a) In this case, for a buffering capacity, if we want to select the best buffer, we should ensure that the buffer's pKa approaches the desired pH, therefore, since the buffer NH3/NH4Cl has a pKa of 9.25 that is very close to the desired pH of 9.10, we can pick it as the best choice.

b) In this case, we use the Henderson-Hasselbach equation in order to compute the molar ratio:

$pH=pKa+log(\frac{[Base]}{[Acid]} )\\\\log(\frac{[Base]}{[Acid]} )=9.10-9.25=-0.15\\\\\frac{[Base]}{[Acid]} =10^{-0.15}\\\\\frac{[Base]}{[Acid]} =0.708$

c) Finally, for the ratio of masses, we use the molar mass of both ammonia as the base (17 g/mol) and ammonium chloride as the acid (53.45 g/mol) to compute it, assuming 1.00 L as the volume of the solution:

$\frac{m_{Base}}{m_{Acid}} =0.708\frac{molBase}{molAcid}*\frac{17gBase}{1molBase} *\frac{1molAcid}{53.45gAcid}\\ \\\frac{m_{Base}}{m_{Acid}} =0.225$

Regards.

Answer 2

The best choice to create a buffer with pH 9.10 is NH₃/NH₄Cl (pKa=9.25), ratio of molarities and masses for NH₃/NH₄Cl are 0.708 & 0.225 respectively.

How do we calculate the pH of buffer solution?

pH of buffer solution will be calculated by using the Henderson Hasselbalch equation as:

pH = pKa + log([base]/[acid])

• From the above reaction it is clear that valu of pH is directly proportional to the value of pKa. So, the pKa value for NH₃/NH₄Cl is comparatively high which will close to the 9.10 pH.
• Ratio of the molarities for the NH₃/NH₄Cl buffer solution will be calculated by using the Henderson Hasselbalch equation as:

        log([NH₃]/[NH₄Cl]) = 9.10 - 9.25 =

        log([NH₃]/[NH₄Cl]) = -0.15

       [NH₃]/[NH₄Cl] = $10^{-0.15}$ = 0.708

• Ratio of masses for the NH₃/NH₄Cl buffer solution will be calculated by using the below equation as:

        M = n/V, where

        M = molarity

        V = volume = 1L

        n = moles = W(mass) / M(molar mass)

        Mass(NH₃)/Mass(NH₄Cl) = 0.708 {(mol of NH₃×17g of NH₃NH₃) /          

                                                              (mol of NH₄Cl×53.45g of NH₄Cl)

       Mass(NH₃)/Mass(NH₄Cl) = 0.225

Hence required values are calculated above.

To know more about Henderson Hasselbalch equation, visit the below link:
https://brainly.com/question/13651361