CHE 2A Chapter Notes -Hydrogen Peroxide, Chemical Formula, Empirical Formula

• School: UC-Davis
• Department: Chemistry
• Course: CHE 2A
• Professor: A N D R E A S T O U P A D A K I S

Document Summary

Finding empirical and molecular formula from percent composition. % composition = (element mass / compound mass) x 100. If you are given the % composition of a compound, here are the steps for finding the empirical formula: assume you have a 100 g sample. This makes the calculation simple because the percentages will be the same as the number of grams. For example, if 40% of the mass of a compound is oxygen then you calculate you have 40 grams of oxygen: convert grams to moles. Empirical formula is a comparison of the number of moles of a compound so you need your values in moles. Using the oxygen example again, there are 16. 0 grams per mole of oxygen so 40 grams of oxygen would be 40/16 = 2. 5 moles of oxygen. Grams - - - > moles divide the mass given to you by molar mass. Ex . 857g h and 6. 86 g of o.