1 / 12

Drill – 2/7/11

Drill – 2/7/11. What is the molar mass of BF 3 ? What is the molar mass of B 2 F 6 ? What is the ratio between these values?. Empirical Formulas. How would a scientist determine the identity of a substance that they made?. Percent Composition. Mass of element in compound X 100%

camden
Download Presentation

Drill – 2/7/11

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Drill – 2/7/11 • What is the molar mass of BF3? • What is the molar mass of B2F6? • What is the ratio between these values?

  2. Empirical Formulas

  3. How would a scientist determine the identity of a substance that they made?

  4. Percent Composition • Mass of element in compound X 100% Total mass of compound • Repeat for each element in compound • Will add up to 100

  5. Empirical Formula • The symbols for the elements combined in the compound, with subscripts showing the smallest whole-number ratio of the different atoms in the compound. • Ionic = formula unit • Covalent = reduced molecular formula

  6. If you know the percent composition of a compound, then you can determine its empirical formula. • We do this by first assuming we have a 100.0 g sample so that the percentage values can be converted to grams. • We then convert the grams to moles (to account for atoms having different molar masses) • To correct for our assumption of 100.0 g we then divide each number of moles by the smallest number.

  7. What is the empirical formula if a compound contains 32.4% Na, 22.6% S, & 45.0% O? • Mass composition (in 100.0g) = • 32.4 g Na, 22.6 g S, 45.0 g O • Composition in moles = • 32.4 g Na x (1 mol Na / 22.99 g Na) = 1.41 mol Na • 22.6 g S x (1 mol S / 32.07 g S) = 0.705 mol S • 45.0 g O x (1 mol O / 16.00 g O) = 2.81 mol O • Smallest whole-number mole ratio • 1.41 mol Na / .705 = 2.00 mol Na • .705 mol S / .705 = 1.00 mol S • 2.81 mol O / .705 = 3.99 mol O

  8. Percent Composition Mass Composition Composition in moles Smallest whole-number mole ratio

  9. A compound’s empirical formula can also be used to determine its molecular formula. • x (empirical formula) = molecular formula • x = whole-number factor

  10. Determine the molecular formula of the compound with an empirical formula of CH and a mass of 78.11 amu. • Molecular formula mass = 78.11 amu • Empirical formula mass = C + H = 12.01 amu + 1.01 amu = 13.02 amu x (empirical formula) = molecular formula x (13.02 amu) = 78.11 amu x = 78.11 amu / 13.02 amu = 5.999 So… CH  C6H6

  11. In the green workbook: • Pg 67 #1 b • Pg 77 #1 a & b • Pg 79 #1 a & b • Pg 89 #1 a & b • Pg 94 #1 a & b

  12. Drill – 2/8/11 • What is the percent composition of each element in Fe2O3?

More Related