Chapter 11, Problem 75A

(a)

Interpretation Introduction

Interpretation:

The balance chemical equation for the given reaction if each square represents element M and circle represents element N needs to be determined.

Concept introduction:

The mole concept provides the relation between moles, mass and molar mass. The mathematical expression of mole concept can write as:

$\text{Mole =}\frac{\text{Mass}}{\text{Molar mass}}$

1 mole of any substance contains $\text{6}\text{.022 }\times {\text{ 10}}^{\text{23}}$ number of particles or atoms or molecules.

Answer to Problem 75A

${\text{3 M}}_{\text{2}}{\text{+ N}}_{\text{2}}\stackrel{}{\to }{\text{ 2 M}}_{\text{3}}\text{N }$

Explanation of Solution

The given figure contains three molecules of each reactant whereas at product side, there are 2 ${\text{N}}_{\text{2}}$ remaining with two ${\text{M}}_{\text{3}}\text{N}$. Thus only one ${\text{N}}_{\text{2}}$ is used. It makes the balance chemical equation as:

${\text{3 M}}_{\text{2}}{\text{+ N}}_{\text{2}}\stackrel{}{\to }{\text{ 2 M}}_{\text{3}}\text{N }$

Interpretation Introduction

(b)

Interpretation:

The moles of M and N present at the start of the reaction if each square is 1 mole of M and each circle is 1 mole of N needs to be determined.

Concept introduction:

A chemical reaction involves the conversion of certain molecules (reactant) to new substance (product) by bond breaking and making. One of the reactant, which is present in limited amount and determines the amount of product, called as limiting reactant. Whereas another reactant is called as excess reactant.

Answer to Problem 75A

If each square is 1 mole of M and each circle is 1 mole of N, there are 6 moles of element M (in the form of 3 moles of ${\text{M}}_{\text{2}}$ ) and 6 moles of element N in 3 moles of ${\text{N}}_{\text{2}}$.

Explanation of Solution

The given figure contains three molecules of each reactant whereas at product side, there are 2 ${\text{N}}_{\text{2}}$ remaining with two ${\text{M}}_{\text{3}}\text{N}$. Thus only one ${\text{N}}_{\text{2}}$ is used. It makes the balance chemical equation as:

${\text{3 M}}_{\text{2}}{\text{+ N}}_{\text{2}}\stackrel{}{\to }{\text{ 2 M}}_{\text{3}}\text{N }$

If each square is 1 mole of M and each circle is 1 mole of N, there are 6 moles of element M (in the form of 3 molesof ${\text{M}}_{\text{2}}$ ) and 6 moles of element N in 3 moles of ${\text{N}}_{\text{2}}$.

Interpretation Introduction

(c)

Interpretation:

The moles of product formed and moles of M and N remaining if each square is 1 mole of M and each circle is 1 mole of N.

Concept introduction:

A chemical reaction involves the conversion of certain molecules (reactant) to new substance (product) by bond breaking and making. One of the reactant, which is present in limited amount and determines the amount of product, called as limiting reactant. Whereas another reactant is called as excess reactant.

Answer to Problem 75A

• ${\text{M}}_{\text{3}}\text{N }$ = 2 moles
• ${\text{N}}_{\text{2}}$ = 2 moles
• N element = 4 moles

Explanation of Solution

The balance chemical equation as:

${\text{3 M}}_{\text{2}}{\text{+ N}}_{\text{2}}\stackrel{}{\to }{\text{ 2 M}}_{\text{3}}\text{N }$

If each square is 1 mole of M and each circle is 1 mole of N, there are 6 moles of element M (in the form of 3 moles of ${\text{M}}_{\text{2}}$ ) and 6 moles of element N in 3 moles of ${\text{N}}_{\text{2}}$. At the product side, there are two moles of ${\text{M}}_{\text{3}}\text{N }$ and two moles of ${\text{N}}_{\text{2}}$ remain unreacted.

Interpretation Introduction

(d)

Interpretation:

The limiting and excess reagent needs to be identified, if each square is 1 mole of M and each circle is 1 mole of N.

Concept introduction:

A chemical reaction involves the conversion of certain molecules (reactant) to new substance (product) by bond breaking and making. One of the reactant, which is present in limited amount and determines the amount of product, called as limiting reactant. Whereas another reactant is called as excess reactant.

Answer to Problem 75A

• Limiting reactant = ${\text{M}}_{\text{2}}$
• Excess reactant = ${\text{N}}_{\text{2}}$

Explanation of Solution

The balance chemical equation as:

${\text{3 M}}_{\text{2}}{\text{+ N}}_{\text{2}}\stackrel{}{\to }{\text{ 2 M}}_{\text{3}}\text{N }$

If each square is 1 mole of M and each circle is 1 mole of N, there are 6 moles of element M (in the form of 3 moles of ${\text{M}}_{\text{2}}$ ) and 6 moles of element N in 3 moles of ${\text{N}}_{\text{2}}$. At the product side, there are two moles of ${\text{M}}_{\text{3}}\text{N }$ and two moles of ${\text{N}}_{\text{2}}$ remain unreacted.

Here at the product side ${\text{N}}_{\text{2}}$ molecules remain therefore it must be excess reactant whereas a limiting reactant consume completely during the reaction and determines the amount of product formed. Thus ${\text{M}}_{\text{2}}$ must be limiting reactant.