# What is the empirical formula of something that is made of 31g of phosphorous and 35g of Cl?

Sep 18, 2016

The empirical formula is $\text{PCl}$.

#### Explanation:

The empirical formula is the simplest whole-number ratio of atoms in a compound.

Your compound contains 31 g $\text{P}$ and 35 g $\text{Cl}$.

$\text{Moles of P" = 31 color(red)(cancel(color(black)("g P"))) × "1 mol P"/(30.97color(red)(cancel(color(black)( "g P")))) = "1.00 mol P}$

$\text{Moles of Cl "= 35 color(red)(cancel(color(black)("g Cl"))) × "1 mol Cl"/(35.45 color(red)(cancel(color(black)("g Cl")))) = "0.987 mol Cl}$

From this point on, I like to summarize the calculations in a table.

$\text{Element"color(white)(Ag) "Mass/g"color(white)(X) "Moles"color(white)(Xll) "Ratio"color(white)(mll)"Integers}$
stackrel(————————————————————)(color(white)(m)"P" color(white)(XXXmm)31 color(white)(Xml)1.00 color(white)(Xmll)1.01color(white)(mmmm)1)
$\textcolor{w h i t e}{m} \text{Cl" color(white)(XXXXll)35 color(white)(mml)} 0.987 \textcolor{w h i t e}{X m l} 1 \textcolor{w h i t e}{m m m m m l} 1$

There is 1 mol of $\text{P}$ for 1 mol of $\text{Cl}$.

The empirical formula is $\text{PCl}$.

Here is a video that illustrates how to determine an empirical formula.