Empirical formulas from composition

Tables 2-2 and 2-3 summarize the procedure for determining an empirical formula from composition data and vice versa.

EXAMPLE F.2 Determining the empirical formula from mass percentage composition... 

The first step is to determine the empirical formula from the percent composition data. 

Determine the simplest (empirical) formula from the % composition data. 

Be able to calculate the empirical formula from percent composition data or quantities from chemical analysis. 

To determine an empirical formula from a percent composition, do the following ... 

If 1.00 g of the unknown contains 0.817 g carbon, the mass percent of carbon is 81.7 percent, leaving the remaining 18.3 percent as hydrogen. Therefore, we need to use the procedures for determining an empirical formula from a percentage composition. The problem will progress as follows (remember with percents, assume a 100 g sample) ... 

Finding a Compound s Empirical Formula from Percentage Composition Part A... 

In the previous section the problems presented a chemical formula and asked for the percent composition. There is a method for going from percent composition to chemical formula however, you will obtain only the empirical formula from this. The three steps in determining the empirical formula of a compound from the percent composition are as follows ... 

We can find the empirical formula from percent composition data. The empirical formula represents a ratio therefore, it does not depend on the size of the sample under consideration. Because the empirical formula reflects a mole ratio, and percent composition data are given in terms of mass, we have to convert the masses to moles. We then convert the mole ratio, which is unlikely to be an integral ratio, to the smallest possible whole-number ratio, from which we write the empirical formula. 

The steps we take to obtain an empirical formula from percent composition data are given in the left column (Steps) that follows. In the right column (Example), the empirical formula of a compound containing 39.2% phosphorus and 60.8% sulfur is calculated. 

We can obtain an empirical formula from mass data instead of a percent composition. 

Determine an empirical formula from each of the following sets of percent composition data ... 

Example of the Calculation of the Percentage Composition and the Empirical Formula, from the. Data of Analysis... 

Empirical Formula.—The calculation of the empirical formula from the percentage composition is as follows ... 

Determine a compound s empirical formula from its percentage composition. 

Let s say that you want to find an empirical formula from the percentage composition. First, convert the mass percentage of each element to grams. Second, convert from grams to moles using the molar mass of each element as a conversion factor. (Keep in mind that a formula for a compound can be read as a number of atoms or as a number of moles.) Third, as shown in Sample Problem C, compare these amounts in moles to find the simplest whole-number ratio among the elements in the compound. 

Sample Problem G Determining an Empirical Formula from Percentage Composition... 

For more practice calculating an empirical formula from percent composition, go to Supplemental Practice Problems in Appendix A. 

To find the empirical formula from the percent mass composition, you assume that you have a 100 gram sample. Now the percent translates directly to grams. 

H.21 (a) We can find the empirical formulas from the percent compositions. 

J.9 Since X turns litmus red and conducts electricity poorly, it is a weak acid. We can find the empirical formula from the percent composition. 

Peroxyacylnitrate (PAN) is one of the components of smog. It is a compound of C, H, N, and O. Determine the percent composition of oxygen and the empirical formula from the following percent composition by mass 19.8 percent C, 2.50 percent H, 11.6 percent... 

---