Chapter 5, Problem 5.112P

(a)

Interpretation Introduction

Interpretation:

The volume of ${\text{O}}_{\text{2}}$ required for the combustion of four volumes of the compound containing only carbon, hydrogen and nitrogen is to be calculated.

Concept introduction:

In a balanced chemical equation, the total mass of reactants and products are equal in a balanced chemical equation, thus, it obeyed the law of conservation of mass. Also, the amounts of substances in a balanced chemical reaction are stoichiometrically equivalent to each other.

The coefficients in the balanced equation tell about the number of molecules or moles of each reactant and product involved in the reaction.

Stoichiometry of a reaction is utilized to determine the amount of any species in the reaction by the relationship between the reactants and products.

Consider the general reaction,

  $\text{A}+2\text{B}\to 3\text{C}$

One mole of $\text{A}$ reacts with two moles of $\text{B}$ to produce three moles of $\text{C}$. The stoichiometric ratio between A and B is 1:2, the stoichiometric ratio between A and C is 1:3 and the stoichiometric ratio between B and C is 2:3.

(b)

Interpretation Introduction

Interpretation:

The empirical formula of the compound is to be calculated.

Concept introduction:

The formula to calculate moles is:

  $\text{Amount}\left(\text{mol}\right)=\frac{\text{mass}}{\text{molar mass}}$        (1)

An empirical formula gives the simplest whole number ratio of atoms of each element present in a compound. The molecular formula tells the exact number of atoms of each element present in a compound.

Following are the steps to determine the molecular formula of a compound.

Step 1: Add the molar mass of each element multiplied by its number of atoms present in the empirical formula to obtain the empirical formula mass for the compound.

Step 2: Divide the molar mass of the compound by its empirical formula mass to obtain the whole number. The formula to calculate the whole number multiple is as follows:

  $\text{Whole}-\text{number multiple}=\frac{\text{Molar mass of compound}}{\text{Empirical formula mass}}$        (2)

Step 3: Multiply the whole number with the subscript of each element present in the empirical formula. This gives the molecular formula of the compound.