Chapter 3, Problem 3.1P

Interpretation Introduction

Interpretation:

Write a balance equation for the reaction of element A (red spheres) with element B (green spheres).

Concept Introduction:

Number of spheres represents the number of molecules.

Answer to Problem 3.1P

$9{\text{A}}_{\text{2}}+6\text{B}\to 6{\text{A}}_{\text{3}}\text{B}$

Or

$3{\text{A}}_{\text{2}}+2\text{B}\to 2{\text{A}}_{\text{3}}\text{B}$

Given:

Element $\text{A}$represents red sphere and element $\text{B}$represents green spheres.

Explanation of Solution

In left box, reactant side, two red spheres are stick together and green spheres are independent. Therefore, box contain molecules of ${\text{A}}_{\text{2}}$and $\text{B}$.

In right box, product side, compound formed by arrangement of A and B in the ratio of 3:1 is present. Therefore, box contain molecules of compound ${\text{A}}_{\text{3}}\text{B}$.

${\text{A}}_{\text{2}}+\text{B}\to {\text{A}}_{\text{3}}\text{B}$

By trial and error method, it can be found out ${\mathrm{A}}_2$has $3$molecule, $\text{B}$has $2$molecule while ${\text{A}}_{\text{3}}\text{B}$has $2$molecule.

Now balance equation can be written as:

$9{\text{A}}_{\text{2}}+6\text{B}\to 6{\text{A}}_{\text{3}}\text{B}$

Or, it can be simplified as follows:

$3{\text{A}}_{\text{2}}+2\text{B}\to 2{\text{A}}_{\text{3}}\text{B}$

Conclusion

Number of atom in reactant side = Number of atomic product side. Atoms are conserved during chemical reaction.