Step 1

$\left[\mathrm{HA}\right]\mathbf{}\mathbf{=}\frac{\mathbf{30}\mathbf{}\overline{)\mathbf{mg}}\mathbf{}\mathbf{\times}{\displaystyle \frac{{\mathbf{10}}^{\mathbf{-}\mathbf{3}}\mathbf{}\overline{)\mathbf{g}}}{\mathbf{1}\mathbf{}\overline{)\mathbf{mg}}}}\mathbf{\times}{\displaystyle \frac{\mathbf{1}\mathbf{}\mathbf{mol}}{\mathbf{378}\mathbf{.}\mathbf{85}\mathbf{}\overline{)\mathbf{g}}}}}{\mathbf{1}\mathbf{}\overline{)\mathbf{mL}}\mathbf{}\mathbf{\times}{\displaystyle \frac{{\mathbf{10}}^{\mathbf{-}\mathbf{3}}\mathbf{}\mathbf{L}}{\mathbf{1}\mathbf{}\overline{)\mathbf{mL}}}}}$** = 0.0792 M**

Step 2

Step 3

**${\mathbf{K}}_{\mathbf{a}}\mathbf{}\mathbf{=}\mathbf{}\frac{\mathbf{2}\mathbf{.}\mathbf{1}\mathbf{\times}{\mathbf{10}}^{\mathbf{-}\mathbf{14}}}{\mathbf{8}\mathbf{.}\mathbf{33}\mathbf{\times}{\mathbf{10}}^{\mathbf{-}\mathbf{9}}}$ = 2.521x10 ^{-6}**

Step 4

${\mathbf{K}}_{\mathbf{a}}\mathbf{}\mathbf{=}\frac{\left[{A}^{-}\right]\left[{H}_{3}{O}^{+}\right]}{\left[\mathrm{HA}\right]}\phantom{\rule{0ex}{0ex}}{\mathbf{K}}_{\mathbf{a}}\mathbf{}\mathbf{=}\frac{\left(x\right)\left(x\right)}{\mathbf{0}\mathbf{.}\mathbf{0792}\mathbf{}\mathbf{-}\mathbf{}\mathbf{x}}$

$\frac{\left[\mathrm{HA}\right]}{{\mathbf{K}}_{\mathbf{a}}}\mathbf{=}\frac{\mathbf{0}\mathbf{.}\mathbf{0792}}{\mathbf{2}\mathbf{.}\mathbf{521}\mathbf{\times}{\mathbf{10}}^{\mathbf{-}\mathbf{6}}}\mathbf{>}\mathbf{>}\mathbf{>}\mathbf{}\mathbf{500}$

Papaverine hydrochloride (abbreviated papH^{+}Cl^{-}; molar mass = 378.85 g/mol) is a drug that belongs to a group of medicines called vasodilators, which cause blood vessels to expand, thereby increasing blood flow. This drug is the conjugate acid of the weak base papaverine (abbreviated pap; K_{b} = 8.33 X 10 ^{-9} at 35.0°C). Calculate the pH of a 30.0-mg/mL aqueous dose of papH^{+}Cl^{-} prepared at 35.0°C. K _{w} at 35.0°C is 2.1 X 10 ^{-14}.

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Ka and Kb concept. You can view video lessons to learn Ka and Kb. Or if you need more Ka and Kb practice, you can also practice Ka and Kb practice problems.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Lapeyrouse's class at UCF.

What textbook is this problem found in?

Our data indicates that this problem or a close variation was asked in Chemistry: An Atoms First Approach - Zumdahl Atoms 1st 2nd Edition. You can also practice Chemistry: An Atoms First Approach - Zumdahl Atoms 1st 2nd Edition practice problems.