Question

Write equations for the following acid- base reactions. Use the information in Table 2.2 or Appendix 4 to predict whether the equilibrium will favor the reactants or the products.

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

(j)

Short answer

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

(j)

Step-by-step solution

Conjugate acid-base pair

The residual part of acid after losing a proton (H⁺) will have a tendency to accept a proton (H⁺) . Therefore, it will behave as a base. These pairs of substances which differ from one another by a proton (H⁺) are known as conjugate acid-base pairs. Consider a general example of an acid:

Ka  and  pKa

K_a is known as the acid dissociation constant and its value indicates the relative strength of the acid. pK_a is defined as the negative logarithm (base 10 ) of K_a. Mathematically, pK_a = -logK_a. pK_a value of strong acids is usually zero or even negative while the pK_a value of weaker acids are greater than 4.

K_b is known as the base dissociation constant and its value indicates the relative strength of the base. pK_b is defined as the negative logarithm (base 10) of K_b. Mathematically, pK_b= -logK_b.

Equilibrium positions of acid-base reactions

The formation of weaker acid and weaker base is favored by the acid-base equilibrium. Larger pK_a means weaker is the acid while larger pK_b means weaker is the base. Both the weaker acid and weaker base exist as either reactants or products and they are always present on the same side of the equation.

Prediction of equilibrium

(a)

The weaker acid and weaker base are both present in the product side, hence the equilibrium will favor the products.

(b)

The weaker acid and weaker base are both present in the reactant side, hence the equilibrium will favor the reactants.

(c)

The weaker acid and weaker base are both present in the product side, hence the equilibrium will favor the products.

(d)

The weaker acid and weaker base are both present in the reactant side, hence the equilibrium will favor the reactants.

(e)

The weaker acid and weaker base are both present in the product side, hence the equilibrium will favor the products.

(f)

The weaker acid and weaker base are both present in the product side, hence the equilibrium will favor the products.

(g)

The weaker acid and weaker base are both present in the product side, hence the equilibrium will favor the products.

(h)

The weaker acid and weaker base are both present in the product side, hence the equilibrium will favor the products.

(i)

The weaker acid and weaker base are both present in the product side, hence the equilibrium will favor the products.

(j)

The weaker acid and weaker base are both present in the product side, hence the equilibrium will favor the products.