Q39P - Chemistry: Molecular Nature Of Matter And Change

Question

(a) A Brønsted-Lowry acid-base reaction proceeds in the net direction in which a stronger acid and stronger base form a weaker acid and weaker base. Explain

(b) The molecular scene at the right depicts an aqueous solution of two conjugate acid-base pairs: HA/A and HB/B. The base in the first pair is represented by red spheres and the base in the second pair by green spheres; solvent molecules are omitted for clarity. Which is the stronger acid? Stronger base? Explain.

                                                   

Step-by-Step Solution

Answer

(a) Strong acids and bases dissociate, whereas weak acids and bases dissociate only partially.

(b)  is the stronger base and HB is the stronger acid

Step 1: Concept Introduction

The natural equilibrium between acids and alkalis in the organism; "the blood is slightly alkaline with a normal acid-base balance in the body" (physiology)

Step 2: Which a stronger acid and stronger base form a weaker acid and weaker base. Explain

(a)

Weak acids and bases only partially dissociate, whereas strong acids and bases entirely dissociate. As a result, in a Bronsted-Lowry acid-base reaction, the net direction is from strong acids and bases to weaker conjugates.

As a result, whereas weak acids and bases dissociate only partially. 

Step 3: Which is the stronger acid? Stronger base? Explain.

(b)

 The net direction of a Bronsted-Lowry acid-base reaction is from strong acids and bases to weaker conjugates, as shown in (a). The red spheres stand for ${\mathrm{A}}^{-}$.${\mathrm{B}}^{-}$  is represented by the green spheres. The HA and HB are the spheres with white spheres attached to them, respectively.

The reaction would look like,

$\mathrm{HA} + {\mathrm{B}}^{-} \mathrm{֏} {\mathrm{A}}^{-} + \mathrm{HB}$

 

Remember that the net direction will be weak to strong. As a result, because weak acids and bases are consumed as reactants in the net reaction, there will be more of them created than strong acids and bases. To identify them, count the number of spheres in the beaker.

                                           

We can see that the beaker, ${\mathrm{A}}^{-}$ and HB have less molecules.

As a result, the stronger base is ${\mathrm{A}}^{-}$ , while the stronger acid is HB .