Chapter 5, Problem 5.103P

Interpretation Introduction

Interpretation:

The molecular formula of the anesthetic gas that contains $64.81\text{ \%}$ carbon, $13.60\text{ \%}$ hydrogen, and $21.59\text{ \%}$ oxygen by mass at $25°\text{C}$ and $0.420\text{atm}$ is to be determined.

Concept introduction:

The formula to find an amount(mol) 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.