PPT-Empirical Formula

based on data Usually composition data Why is it important to be able to calculate the empirical formula Penicillin Antibiotic Discovered about 80 years ago Paved the way for other antibiotics to be created which increased life expectancy. Chemical Formula Relationships. Number of Atoms in a Formula. In writing the formula of a substance, subscript numbers are used to indicate the number of atoms or groups of atoms of each element in the formula unit.. . vs. . Empirical Formula. Different compounds can have the . same. empirical formula. but . different. molecular formulas. .. Empirical . Formula is a . reduced. . form of Molecular formula . Molecular Formula and Empirical Formula. Molecular Formulas. Let’s use those mole conversions!. Empirical formula . tells you the lowest ratio of atoms within a molecule. Molecular formula . tells you the actual ratio of atoms within a molecule. Q- a compound is found to contain the following % by mass: 69.58% Ba, 6.090% C, 24.32% O. What is the simplest (i.e. empirical) formula?. Step 1. : imagine that you have 100 g of the substance. Thus, % will become mass in grams. E.g. 69.58 % Ba becomes 69.58 g Ba. (Some questions. You should know this for the quiz!. Empirical and Molecular Formulae. Empirical Formula. If needed, change % to g.. Do . a molar conversion to change from . g. mol. Divide each of these numbers by the smallest number. Objectives. To learn how to work out the percentage composition by weight of a compound. To use percentage composition to work out empirical formulae. Percentage compositions. This means what percentage of each element is present in a compound, and therefore tells you what masses of each element are present in any given mass of a compound. . Molecular Formulas. Let’s use those mole conversions!. Empirical formula . tells you the lowest ratio of atoms within a molecule. Molecular formula . tells you the actual ratio of atoms within a molecule. Percent Composition. . Percent Composition – . the percentage by mass of each element in a compound . Percent =. _______. Part. Whole. x 100%. So…. Percent composition. of a compound or =. molecule. Percent Composition, . Empirical/ Molecular . Formula . Finishing Up Ch. 10. In 1811, Avogadro proposed a hypothesis:. Volumes of gases at the same temp and pressure have the same number of particles. Percent Composition. Percent . Composition – . the . percentage . by mass of . each . element in a . compound (*note: not the ratio of elements in the compound). Law of Definite Proportions . – compounds always contain the same proportions of elements by mass.. I. Percent Composition. Think about this:. How would you find the percent of boys in our class?. # of boys (part)____. x 100% . Total # of students (whole). I. Percent Composition. . Lowest whole # ratio . H. 2. O. 2. (hydrogen peroxide) is it a empirical Formula?. No, you can reduce it to HO . . H. 2. O. 2 . is the molecular formula. Molecular formula shows the way the molecule is actually found in nature.. Percent Composition. Breaks down the amount of an element in a compound by percentage. Total mass of element / total mass of compound. Result will always be a decimal. Multiply by 100 to get the final percentage. Percent Composition. ~percent by mass of atoms present in a compound. = (mass of atom). . (total molar mass) x 100. water is . 88.81 . % Oxygen and . 11.19 . % Hydrogen. O- 16.00/18.016 x 100 = . 88.81 .