Chapter 3.2, Problem 3.9AFP

Interpretation Introduction

Interpretation:

The empirical formula and the name of the compound that contains $1.23\text{ g}$ of hydrogen $\left(\text{H}\right)$, $12.64\text{ g}$ of phosphorous $\left(\text{P}\right)$, and $26.12\text{ g}$ of oxygen $\left(\text{O}\right)$ are to be determined.

Concept introduction:

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

Following are the steps to determine the empirical formula of a compound when the masses of each element are given,

Step 1: Divide mass of each element by its molar mass to convert the mass of the element to moles. The formula to calculate moles from the mass is as follows:

$\text{Amount}\left(\text{mol}\right)=\left(\text{Given mass}\left(\text{g}\right)\right)\left(\frac{1\text{ mol}}{\text{No}\text{. of grams}}\right)$

Step 2: The number of moles of the elements is the fractional amounts, thus, write the calculated amount $\left(\text{mol}\right)$ of each element as the subscript of the element’s symbol to obtain a preliminary formula for the compound.

Step 3: Convert the moles of each element to the whole number subscripts. The steps for this math conversion are as follows:

(a) Each subscript is divided by the smallest subscript.

(b) If the whole number is not obtained after division, multiply the obtained subscripts by the smallest integer.