# Problem: A student dissolves 0.0100 mole of an unknown weak base in 100.0 mL water and titrates the solution with 0.100 M HNO3. After 40.0 mL of 0.100 M HNO 3 was added, the pH of the resulting solution was 8.00. Calculate the Kb value for the weak base.

###### FREE Expert Solution

Recall:

$\overline{){{\mathbf{K}}}_{{\mathbf{b}}}{\mathbf{=}}\frac{\mathbf{products}}{\mathbf{reactants}}}$

We shall construct an ICF Chart first:

0.004 moles

We shall construct an ICE Chart based on the following reactions with water:

HB+ + H2O ⇌ B + H3O+

$\overline{){\mathbf{pOH}}{\mathbf{=}}{\mathbf{14}}{\mathbf{-}}{\mathbf{pH}}}$

${\mathbf{pOH}}{\mathbf{=}}{\mathbf{14}}{\mathbf{-}}{\mathbf{8}}{\mathbf{=}}$6.00

$\overline{)\mathbf{\left[}{\mathbf{OH}}^{\mathbf{-}}\mathbf{\right]}{\mathbf{=}}{{\mathbf{10}}}^{\mathbf{-}\mathbf{pOH}}}$

$\mathbf{\left[}{\mathbf{OH}}^{\mathbf{-}}\mathbf{\right]}{\mathbf{=}}{{\mathbf{10}}}^{\mathbf{-}\mathbf{6}}$

Calculate the concentrations:

Total volume = 100 mL WB + 40 mL HNO3 = 140 mL

0.0286 M

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###### Problem Details

A student dissolves 0.0100 mole of an unknown weak base in 100.0 mL water and titrates the solution with 0.100 M HNO3. After 40.0 mL of 0.100 M HNO 3 was added, the pH of the resulting solution was 8.00. Calculate the Kb value for the weak base.

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 Acid and Base Titration Curves concept. You can view video lessons to learn Acid and Base Titration Curves. Or if you need more Acid and Base Titration Curves practice, you can also practice Acid and Base Titration Curves practice problems.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Billman's class at Abilene Christian University.

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.