The base imidazole has a Kb of 1.0 ×10^-7 at 25^∘ C. In what volumes should 0.02 M -HCl and 0.02

step 1 So in this station, B plus H positive gives BH positive, BH positive. So v. 0 .02 divided by 120

The base imidazole has a Kb of 1.0 ×10^-7 at 25^∘ C. In what...

The base imidazole has a $K_{b}$ of $1.0 \times 10^{-7}$ at $25^{\circ} \mathrm{C}$. In what volumes should $0.02 \mathrm{M}$ $-\mathrm{HCl}$ and $0.02 \mathrm{M}$ imidazole be mixed to make $120 \mathrm{ml}$ of a buffer at $\mathrm{pH}=7$ ? (a) $60 \mathrm{ml}, 60 \mathrm{ml}$ (b) $40 \mathrm{ml}, 80 \mathrm{ml}$ (c) $30 \mathrm{ml}, 90 \mathrm{ml}$ (d) $20 \mathrm{ml}, 100 \mathrm{ml}$

The base imidazole has a $K_{b}$ of $1.0 \times 10^{-7}$ at $25^{\circ} \mathrm{C}$. In what volumes should $0.02 \mathrm{M}$ $-\mathrm{HCl}$ and $0.02 \mathrm{M}$ imidazole be mixed to make $120 \mathrm{ml}$ of a buffer at $\mathrm{pH}=7$ ?
(a) $60 \mathrm{ml}, 60 \mathrm{ml}$
(b) $40 \mathrm{ml}, 80 \mathrm{ml}$
(c) $30 \mathrm{ml}, 90 \mathrm{ml}$
(d) $20 \mathrm{ml}, 100 \mathrm{ml}$

Key Concepts

Buffer Solutions

A buffer solution is composed of a weak acid and its conjugate base or a weak base and its conjugate acid. Such solutions are designed to resist changes in pH when small amounts of acids or bases are added, making them essential in many chemical and biological systems where pH control is critical.

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation provides a relationship between the pH of a buffer solution, the pKa of the weak acid (or relating pKb for a weak base by converting it), and the ratio of the concentrations of the conjugate base to the acid. This equation is a key tool for predicting the pH of a buffer and for designing buffers with a desired pH.

Acid-Base Equilibrium

Acid-base equilibrium describes the reversible reactions between acids and bases where they partially dissociate or combine with their conjugate species. Understanding this concept is fundamental in predicting how the addition of an acid or a base will affect the overall system and how buffer systems maintain stability.

Relationship between pKa and pKb

For conjugate acid-base pairs, there is a direct relationship between the acid dissociation constant (Ka) and the base dissociation constant (Kb) expressed through the water ionization constant (Kw). This relationship (pKa + pKb = pKw) is crucial when working with buffer solutions involving a weak base and its conjugate acid, as it allows one to convert between pKa and pKb for effective use of the Henderson-Hasselbalch equation.

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