# Problem: Calculate the ratio [NH3] / [NH4+] in ammonia/ammonium chloride buffered solutions with the following pH values:a. pH = 9.00

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###### FREE Expert Solution

We’re being asked to calculate the ratio [NH3]/[NH4+] in ammonia/ammonium chloride buffered solutions for ph 9.00.

In an ammonia/ammonium chloride buffered solution, ammonia, NH3 is the weak base and the ammonium ion, NH4+ is its conjugate acid.

Recall that for buffers the pH can be determined using the Henderson-Hasselbalch equation:

where:

[NH3] = concentration of the weak base, NH3

[NH4+] = concentration of conjugate acid, NH4

Since we're given the pH, we can solve for the ratio:  [NH3]/[NH4+]

But first, we need to determine Ka, Since ammonia is a weak base:

Kb = 1.76 x 10-5 (can be found in textbooks or online)

Recall that we can solve Kfrom Kb using the equation:

$\overline{){{\mathbf{K}}}_{{\mathbf{w}}}{\mathbf{=}}{{\mathbf{K}}}_{{\mathbf{a}}}{\mathbf{×}}{{\mathbf{K}}}_{{\mathbf{b}}}}\phantom{\rule{0ex}{0ex}}\overline{){{\mathbf{K}}}_{{\mathbf{a}}}{\mathbf{=}}\frac{{\mathbf{K}}_{\mathbf{w}}}{{\mathbf{K}}_{\mathbf{b}}}}$

**Kw = 1.0 x 10-14 at 25°C (value can be found in textbooks or online)

###### Problem Details

Calculate the ratio [NH3] / [NH4+] in ammonia/ammonium chloride buffered solutions with the following pH values:

a. pH = 9.00