Chapter 19, Problem 19.145P

(a)

Interpretation Introduction

Interpretation:

The scene which shows buffer has to be shown.

Concept introduction:

Buffer solution:

The solution which is capable of maintaining it’s $\text{pH}$ almost constant when a little amount of acid or base is added to it, is known as buffer solution. They are mainly mixture of weak acid and its conjugate base or vice versa.

Henderson-Hasselbalch Equation:

This equation is used to determine the $\text{pH}$ of a buffer solution. ${\text{K}}_{\text{a}}$ is the given quantity I.e. acid dissociation constant. It is done for a given concentration of acid and its conjugate base.

  $\text{pH=}{\text{pK}}_{\text{a}}\text{+}\text{log}\frac{\left[\text{salt}\right]}{\left[\text{acid}\right]}$

$p{K}_a$:

${\text{pK}}_{\text{a}}$ is the negative log of acid dissociation constant that determines the strength of acid. Lower the ${\text{pK}}_{\text{a}}$ value stronger is the acid.

${\text{pK}}_{\text{a1}}$ is the 1^st dissociation constant for the acid and ${\text{pK}}_{\text{a2}}$ is the 2^nd dissociation constant of the acid.

(b)

Interpretation Introduction

Interpretation:

$\text{pH}$ of each solution has to be calculated.

Concept introduction:

pH:

$\text{pH}$ is a scale used to specify how acidic or basic a solution is. It ranges from $0-14$. $\text{pH}$ $7.0$ is considered as neutral solution, $\text{pH}$ more than $7.0$ is taken as basic solution whereas $\text{pH}$ less than $7.0$ is considered as acidic solution (at ${\text{25}}^{\text{ο}}\text{C}$). It is the measurement of activity of free ${\text{H}}^{\text{+}}$ and ${\text{OH}}^{\text{-}}$ in solution.

Buffer solution:

The solution which is capable of maintaining it’s $\text{pH}$ almost constant when a little amount of acid or base is added to it is known as buffer solution. They are mainly mixture of weak acid and its conjugate base or vice versa.

Henderson-Hasselbalch Equation:

This equation is used to determine the $\text{pH}$ of a buffer solution. ${\text{K}}_{\text{a}}$ is the given quantity i.e. acid dissociation constant. It is done for a given concentration of acid and its conjugate base.

  $\text{pH=}{\text{pK}}_{\text{a}}\text{+}\text{log}\frac{\left[\text{salt}\right]}{\left[\text{acid}\right]}$

$p{K}_a$:

${\text{pK}}_{\text{a}}$ is the negative log of acid dissociation constant that determines the strength of acid. Lower the ${\text{pK}}_{\text{a}}$ value stronger is the acid.

${\text{pK}}_{\text{a1}}$ is the 1^st dissociation constant for the acid and ${\text{pK}}_{\text{a2}}$ is the 2^nd dissociation constant of the acid.

(c)

Interpretation Introduction

Interpretation:

The scenes have to be arranged considering them in weak acid strong base titration situation.

Concept introduction:

Titration:

Titration is a quantitative chemical analysis to determine the concentration of an identified analyte. The titrant is the reagent which is prepared as a standard solution of known concentration volume. The titrant reacts with the analyte to determine the analyte’s concentration. The volume of the titrant reacting with analyte is called the titration volume.

Equivalence point:

Equivalence point in the titration reaction is the point where the amount of titrant added is absolutely enough to neutralize completely the analyte. The moles of titrant and the moles of analyte are same at this point.

pH:

$\text{pH}$ is a scale used to specify how acidic or basic a solution is. It ranges from $0-14$. $\text{pH}$ $7.0$ is considered as neutral solution, $\text{pH}$ more than $7.0$ is taken as basic solution whereas $\text{pH}$ less than $7.0$ is considered as acidic solution (at ${\text{25}}^{\text{ο}}\text{C}$). It is the measurement of activity of free ${\text{H}}^{\text{+}}$ and ${\text{OH}}^{\text{-}}$ in solution.

Weak acid- strong base titration:

Weak acids dissociates very slowly in solution producing less number of ${\text{H}}^{\text{+}}$ and so at first in solution there will be more undissociated acid.

But as strong base is added the ${\text{H}}^{\text{+}}$ in the medium will completely react and then to keep the stable equilibrium more acid is dissociated to give more ${\text{H}}^{\text{+}}$.

At equivalence point there will be only conjugate base of the weak acid and no ${\text{H}}^{\text{+}}$ will remain.

After equivalence point there will be excess added strong base in the medium.

(d)

Interpretation Introduction

Interpretation:

The scene that represents the titration at its equivalence point has to be given.

Concept introduction:

Titration:

Titration is a quantitative chemical analysis to determine the concentration of an identified analyte. The titrant is the reagent which is prepared as a standard solution of known concentration volume. The titrant reacts with the analyte to determine the analyte’s concentration. The volume of the titrant reacting with analyte is called the titration volume.

Equivalence point:

Equivalence point in the titration reaction is the point where the amount of titrant added is absolutely enough to neutralize completely the analyte. The moles of titrant and the moles of analyte are same at this point.