Chapter 23, Problem 112IL

(a)

Interpretation Introduction

Interpretation: The theoretical yield of $\text{2-iodobenzoicacid}$ has to be determined.

Concept introduction:

Number of moles of a substance,

From its given mass is,

$\text{Number of moles}\text{=}\frac{\text{Given}\text{mass}}{\text{Molecular}\text{mass}}$

Theoretical yield is the maximum product yield that can be expected based on the masses of the reactants and the reaction stoichiometry.

2-Iodobenzoic acid is a crystaline solid and it can be prepared from 2-aminobenzoic acid  treated with ${\text{NaNO}}_{\text{2}}\text{, HCl and KI}$.

The reaction can be represnted as follows,

Answer to Problem 112IL

Theoretical yield of benzoic acid is $\text{7}\text{.23 g}$.

Explanation of Solution

From the given data,

$\begin{array}{l}\text{2-amino benzoic acid = 4}\text{.0 g}\\ \text{Molar mass of 2-amino benzoic acid =137}\text{.14 g/mol}\end{array}$

Let’s calculate the number of moles of 2-amino benzoic acid:

$\text{Number of moles = }\frac{\text{Mass}}{\begin{array}{l}\text{Molarmass}\\ \text{=}\frac{\text{4}\text{.0 g}}{\text{137}\text{.14 g/mol}}\\ \text{= 0}\text{.02916 moles}\end{array}}$

From the given:

$\begin{array}{l}{\text{Mass of NaNO}}_{\text{2}}\text{ = 2}\text{.2 g}\\ {\text{Molar mass of NaNO}}_{\text{2}}\text{ = 69 g/mol}\end{array}$

Let’s calculate the number of moles of ${\text{NaNO}}_{\text{2}}$:

$\text{Number of moles =}\frac{\text{Mass}}{\begin{array}{l}\text{Molarmass}\\ \text{=}\frac{\text{2}\text{.2 g}}{\text{69 g/mol}}\\ \text{= 0}\text{.03188 moles}\end{array}}$

From the given:

$\begin{array}{l}\text{Mass of KI = 5}\text{.3 g}\\ \text{Molar mass of KI = 166 g/mol}\end{array}$

Let’s calculate the number of moles of $\text{KI}$:

$\text{Number of moles = }\frac{\text{Mass}}{\begin{array}{l}\text{Molarmass}\\ \text{=}\frac{\text{5}\text{.3 g}}{\text{166 g/mol}}\\ \text{= 0}\text{.03192 moles}\end{array}}$

From the equation , we can see that 1 mole of 2- amino benzoic acid gives 1 mole of 1-iodo benzoic acid .

For this conversion required 1 mole of ${\text{NaNO}}_{\text{2}}$ and 1 mole of $\text{KI}$.

Theoretically produced $\text{0}\text{.02916}$ moles of 2-iodo benzoic acid.

Molar mass of 2-iodobenzoic acid = $\text{248}\text{.02 g/mol}$

$\begin{array}{c}\text{Theoritical yield = Number of moles × Molar mass}\\ \text{= 0}\text{.02916 moles × 248}\text{.02 g/mol}\\ \text{= 7}\text{.23 g}\end{array}$

Therefore, theoretical yield of 2-iodobenzoic acid is $\text{7}\text{.23 g}$.

(b)

Interpretation Introduction

Interpretation: To Check the possibilty of isomers for 2-iodobenzoic acid

Concept introduction:

2-Iodobenzoic acid is a crystaline solid and it can be prepared from 2-aminobenzoic acid  treated with ${\text{NaNO}}_{\text{2}}\text{, HCl and KI}$.

The reaction can be represnted as follows,

Two compounds that have the same molecular formula, but have different structural formulas are called isomers.

Answer to Problem 112IL

No other possible isomers for 2-Iodobenzoic acid.

Explanation of Solution

No other isomers of 2-iodo benzoic acid are possible in this reaction because the ${\text{I}}^{\text{-}}$ group can attach only where amino group was present.

(c)

Interpretation Introduction

Interpretation: The molar mass of the product formed in the given reaction has to be determined. And check whether the calculated molar mass is in reasonable agreement with the theoretical molar mass or not.

Concept introduction:

2-Iodobenzoic acid is a crystaline solid and it can be prepared from 2-aminobenzoic acid  treated with ${\text{NaNO}}_{\text{2}}\text{, HCl and KI}$.

The reaction can be represnted as follows,

Concentration of solutions can be expressed in various terms; molarity is one such concentration expressing term.

Molarity (M) of a solution is the number of gram moles of a solute present in one liter of the solution.

                              $\text{Molarity}\text{=}\frac{\text{Mass}\text{per}\text{litre}}{\text{Molecular }\text{mass}}$

A solution containing one gram mole or $\text{0}\text{.1}$ gram of solute per litre of solution is called molar solution.

Amount of substance (mol) can be determined by using the equation,                     

                       $\text{Number}\text{of}\text{mole}\text{=}\frac{\text{Given}\text{mass}\text{of}\text{the}\text{substance}}{\text{Molar}\text{mass}}$

The molar mass of an element or compound is the mass in grams of 1 mole of that substance, and it is expressed in the unit of grams per mol (g/mol).

Theoretical yield is the maximum product yield that can be expected based on the masses of the reactants and the reaction stoichiometry.

Answer to Problem 112IL

Molar mass of 2-Iodobenzoic acid $\text{253}\text{.012 g/mol}$

There is only $\text{2 \%}$, taking into account titration errors.

Explanation of Solution

From the given,

$\begin{array}{c}\text{Molarity of NaOH = 0}\text{.101 M}\\ \text{Volume of NaOH = 15}\text{.62 mL}\\ \text{= 0}\text{.01562 L}\end{array}$

Let’s calculate the number of mole of $\text{NaOH}$

$\begin{array}{c}\text{Number of moles = Molarity × Volume}\\ \text{= 0}\text{.101 M × 0}\text{.01562 L}\\ \text{=0}\text{.00157 moles}\end{array}$

$\begin{array}{l}\text{Mass = 0}\text{.399 g}\\ \text{number of moles = 0}\text{.00157 moles}\end{array}$

Let’s calculate molar mass of 2-iodo benzoic acid.

$\text{Molar mass =}\frac{\text{Mass}}{\begin{array}{l}\text{Number of moles}\\ \text{=}\frac{\text{0}\text{.399 g}}{\begin{array}{l}\text{0}\text{.00157 moles}\\ \text{= 253}\text{.012 g/mol}\end{array}}\end{array}}$

Theoretical mass 2-Iodobenzoic acid is $\text{248}\text{.02 g/mol}$.

Therefore, there is only $\text{2 \%}$, taking into account titration errors.

We can say that it is in reasonable agreement with theoretical molar mass.