1. An aqueous solution of weak base B of unknown concentration is tritrated with a

known concentration of strong acid, HA.

(a) Write the balanced chemical equation for this acid-base reaction, identifying the
conjugate acid/base pairs.

(b) If the base-dissociation constant of B is 1 × 10^3, what is the pH at the midpoint
of the buffer region? What are the chemical components of the buffer?

(c) Write the balanced chemical equation for the weak acid dissociation in water
occurring at the equivalence point.

(d) At the equivalence point, 500mL of 0.2 M HA(aq) was added to 500mL of the
original B(aq) solution. What is the pH at the equivalence point?

(e) Sketch the titration curve, labeling all axes, the bu?er region, and equivalence
point, along with corresponding pH values.

HA + B ==> BH^+ + A^-

conjugate pairs are as follows:
HA/A^-
B/BH^+

You made a typo on (b). A Kb of 1E3 is NOT a weak base. Therefore, the rest of the problem flawed and the numbers won't mean anything. However, when you correct the Kb value, use the Henderson-Hasselbalch equation to work the buffer part of the problem.

(a) The balanced chemical equation for the acid-base reaction between the weak base B and the strong acid HA can be written as follows:

B(aq) + HA(aq) -> H2O(l) + BA(aq)

In this equation, B represents the weak base, HA represents the strong acid, H2O is water, and BA is the conjugate acid of the weak base B.

(b) To determine the pH at the midpoint of the buffer region and the chemical components of the buffer, we need to consider the ionization of the weak base B and the subsequent formation of a buffer solution.

Since the base-dissociation constant (Kb) of B is given as 1 × 10^3, it indicates that B is a weak base. At the midpoint of the buffer region, the concentrations of the weak base and its conjugate acid are equal.

Let's assume the concentration of the weak base B is x M. After the equilibrium is reached, the concentration of the conjugate acid BA will also be x M.

Using the base-dissociation constant (Kb), we can write the equilibrium expression for the ionization of the weak base:

B(aq) + H2O(l) -> BH+(aq) + OH-(aq)

The equilibrium expression for this reaction is:
Kb = [BH+][OH-] / [B]

Since we assumed that the concentration of B and BA at the midpoint are both x, we substitute x for [B] and [BA] in the equilibrium expression:

Kb = x * x / x

Simplifying, we have:
Kb = x

Given that Kb = 1 × 10^3, we can substitute this value in:
1 × 10^3 = x

Solving for x, we find x = 1 × 10^3 M.

Now, we can determine the pH at the midpoint by calculating the pOH using the concentration of OH- ions:
pOH = -log10[OH-]
pOH = -log10[x]
pOH = -log10[1 × 10^3]
pOH = -3

Since pH + pOH = 14 (at 25°C), we can calculate the pH:
pH = 14 - pOH
pH = 14 - (-3)
pH = 17

Therefore, the pH at the midpoint of the buffer region is 17. The chemical components of the buffer are the weak base B and its conjugate acid BA.

(c) At the equivalence point, the weak acid BA (conjugate acid of the weak base B) undergoes dissociation in water. The balanced chemical equation for this dissociation can be written as follows:

BA(aq) + H2O(l) -> B(aq) + H3O+(aq)

In this equation, BA represents the conjugate acid of the weak base B, B is the weak base, H2O is water, and H3O+ represents hydronium ions.

(d) At the equivalence point, 500 mL of 0.2 M HA(aq) is mixed with 500 mL of the original B(aq) solution. Since the volumes are equal, the concentrations of HA and B will be halved after mixing.

For HA(aq), the final concentration is 0.2 M / 2 = 0.1 M.

To calculate the pH at the equivalence point, we need to determine whether HA or B is in excess. Since HA is a strong acid and B is a weak base, at the equivalence point, B will be in excess.

Thus, we need to calculate the pH of the excess B solution. Given that the concentration of the excess B solution is 1 × 10^3 M (as determined in part (b)), we can use the equilibrium expression for the ionization of the weak base:

B(aq) + H2O(l) -> BH+(aq) + OH-(aq)

At equilibrium, the concentration of OH- will be x M, and the concentration of B will be (1 × 10^3 - x) M.

Using the base-dissociation constant (Kb), we can write the equilibrium expression as follows:

Kb = [BH+][OH-] / [B]
1 × 10^3 = x * OH- / (1 × 10^3 - x)

Since the concentration of OH- in water at 25°C is 1 × 10^-7 M, we can substitute this value in the equation:

1 × 10^3 = x * (1 × 10^-7) / (1 × 10^3 - x)

Solving for x, we find that x = 1 × 10^-7 M.

Now, we can calculate the pOH using the concentration of OH- ions:
pOH = -log10[OH-]
pOH = -log10[x]
pOH = -log10[1 × 10^-7]
pOH = 7

Since pH + pOH = 14 (at 25°C), we can calculate the pH:
pH = 14 - pOH
pH = 14 - 7
pH = 7

Therefore, the pH at the equivalence point is 7.

(e) Unfortunately, as a text-based AI, I am unable to sketch images or draw titration curves. However, I can describe it to you:

A titration curve is a graph that displays the pH of a solution as a function of the volume of the titrant (in this case, the strong acid HA) added. The x-axis represents the volume of the titrant, and the y-axis represents the pH.

At the beginning of the titration, before any titrant is added, the pH will be determined by the weak base B present in the solution. It will be high, above 7.

As the titrant (strong acid HA) is added, the pH will initially increase slowly, as the weak base is neutralized. This region is known as the buffer region. The pH at the midpoint of the buffer region is 17, as calculated in part (b).

Eventually, the pH will start to decrease more rapidly as the equivalence point is approached. The equivalence point occurs when the moles of titrant added equal the original moles of weak base B. At this point, the solution will contain the conjugate acid of the weak base B, BA.

After the equivalence point, the pH will drop sharply due to the excess strong acid in the solution. The pH will be around 7 at the equivalence point, as calculated in part (d).

The titration curve typically shows a steep drop in pH around the equivalence point, highlighting the rapid change in the solution's acidity.

Please note that the actual shape of the titration curve can vary depending on the specific values of the concentrations, volumes, and acid and base strengths involved in the titration.