Chapter 3, Problem 3.115P

(a)

Interpretation Introduction

Interpretation:

The balanced chemical equation corresponding to given reaction scenes is to be written.

Concept introduction:

A balanced chemical equation obeys the law of conservation of mass since the total mass of reactants and products are equal in a balanced chemical equation.

Following are the steps to write a balanced chemical equation.

Step 1: Translate the chemical statement into a skeleton equation. The reactants are the chemical substances that undergo a change, thus, write the reactants on the left side of the yield arrow. The products are the chemical substances that are produced during the chemical change, thus, write the products on the right side of the yield arrow. Put a blank before each formula while beginning the balancing process.

Step 2: Identify the most complex substance and choose an element such that the element must be present only in one reactant and one product. Place the stoichiometric coefficient before the element/elements such that the number of atoms of that element(s) is the same on both sides.

Step 3: Balance the remaining atoms by placing the stoichiometric coefficients before the element/elements such that the number of atoms of that element(s) is the same on both sides. Identify the least complex substance and end with it.

Step 4: In a balanced chemical reaction, the smallest whole number coefficients are most preferred. Hence, adjusting the coefficients in such a way that the smallest whole number coefficients are obtained for each element.

Step 5: Check whether the chemical equation is balanced or not by counting the number of atoms of each element on both sides.

Step 6: Specify the states of matter of each chemical substance present in the balanced chemical equation.

(b)

Interpretation Introduction

Interpretation:

The limiting reactant is to be identified.

Concept introduction:

Limiting reagent is the reactant that is present in the least amount and hence governs the amount of products formed.

In order to determine the limiting reactant firstly a balanced equation is written, then amount of each reactant given is converted to corresponding moles. Further on the basis of the stoichiometric molar ratio by which reactants combine, the amount of product formed from each of the reactants is calculated.

The reactant that forms a lesser amount of product gives us the limiting reactant.

(c)

Interpretation Introduction

Interpretation:

The number of moles of product formed from $3.0\text{ mol }$ of ${\text{B}}_{\text{2}}$ and $5.0\text{ mol }$ of ${\text{AB}}_{\text{2}}$ is to be calculated.

Concept introduction:

In order to determine the limiting reactant firstly a balanced equation is written, then amount of each reactant given is converted to corresponding moles. Further on the basis of the stoichiometric molar ratio by which reactants combine, the amount of product formed from each of the reactants is calculated.

The reactant that forms a lesser amount of product gives us the limiting reactant.

(d)

Interpretation Introduction

Interpretation:

The number of moles of excess reactant remaining after part (c) is to be calculated.

Concept introduction:

Limiting reagent is the reactant that is present in the least amount and hence governs the amount of products formed.

The reagent that is present in the excess amount in the reaction mixture is called excess reactant. It is left unreacted in the reaction mixture after the reaction is completed.