Empirical Formula and Percent Composition Practice

Empirical Formula/Percent Composition Empirical Formula – the lowest whole-number ratio of the elements in a compound. Examples: H2O, CH4, H2SO4 NOT empirical formulas: H2O2, C6H12O6

Simplify the following into their Empirical Formulas: Na2CO3 N2O4 C6H18O3 S2O2 B4H12 P4H10

Steps to Find Empirical Formula: Change percent to grams (assume 100 gram sample) Convert grams to moles Divide each element by the smallest # of moles If needed, multiply ALL by some integer to get whole numbers If we were given grams we would start on step 2 If we were given moles we would start on step 3

Practice Problem %  Empirical Formula NutraSweet is 57.14% C, 6.16% H, 9.52% N, and 27.18% O.  Calculate the empirical formula of NutraSweet. Because 2.5 is too far to round, multiply by 2 C14H18N2O5

Percent Composition Remember that finding the percent composition can be done by: g of element x 100 = g of whole compound