1 / 19

Chemical Quantities

Explore how matter is measured in chemistry through counting and measuring mass and volume. Learn about the concept of a mole, Avogadro’s number, molar mass, gas volumes, percent composition, and empirical and molecular formulas.

jarroda
Download Presentation

Chemical Quantities

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. Chemical Quantities Chapter 7

  2. How Do You Measure Matter? • By Counting • By Measuring • Mass • Volume • In Chemistry, we use a measuring unit called a mole. www.brainybetty.com

  3. What is a Mole? www.brainybetty.com

  4. Well….not exactly! What is a mole and how big is it? • Moleis abbreviatedmol • 1 mole = 6.02 x 1023 representative particles(atoms, particles, molecules, or formula units--ions) akaAvogadro’s number www.brainybetty.com

  5. How many moles of Mg is 1.25 x 1023 atoms of Mg? atoms moles 1.25 x 1023 atoms Mg x 1 mol Mg 6.02 x 1023 atoms Mg = 2.08 x 10-1 mol Mg

  6. How many atoms are in 2.12 mol of propane (C3H8)? Moles molecules atoms 2.12 mol C3H8 x 6.02 x 1023 molecules x 11 atoms 1 mol C3H81 molecule C3H8 = 1.40 x 1025 atoms

  7. The Molar Mass of a Substance • MOLAR MASS: the mass (in grams) of one mole of the substance • What is the molar mass of SO3? 1-S = 1 x 32.1 g = 32.1 g 3-O = 3 x 16.0 g = 48.0 g = 80.1 g • SO3 = 80.1 g/mol www.brainybetty.com

  8. How many grams are in 9.45 mol of N2O3? molesgrams 9.45 mol N2O3 x 76.0 g N2O3 = 718.2 g N2O3 1 mol

  9. What about a mole of gas? • One moleof anygasoccupies22.4 litersat STP • STP = Standard Temperature & Pressure • 273 K • 101.3 kPa • Examples of gases: O2, CO2, N2, H2 www.brainybetty.com

  10. Determine the volume, in liters, of 0.60 mol SO2 gas at STP. moles liters 0.60 mol SO2 x 22.4 L SO2 = 13 L SO2 1 mol

  11. The Mole Road Map Volume Mass MOLE Periodic Table 22.4 liters Gas @STP g/mol 6.02 x 1023 particles (atoms, molecules, formula units, etc.) Avogadro’s Number Rep. Particles

  12. Percent Composition of a Compound • PERCENT COMPOSITION: the percent by mass of each element in a compound % mass of element E = grams of element E x 100% grams of compound

  13. An 8.20 g piece of Mg combines completely with 5.40 g of oxygen to form a compound. What is the percent composition of this compound? % Mg = 8.20 g x 100 % = 60.3% 13.6 g % O = 5.40 g x 100 % = 39.7% 13.6 g

  14. Calculate the percent composition of C3H8. % C = 36.0 g x 100 % = 81.8% 44.0 g % H = 8.0 g x 100 % = 18.2 % 44.0 g www.brainybetty.com

  15. Calculating Empirical Formulas • EMPIRICAL FORMULA:lowest whole number ratio of the atoms of the elements in a compound H2O2 HO N2H4 NH2 CO2 CO2 www.brainybetty.com

  16. What is the empirical formula of a compound that is 25.9% nitrogen and 74.1% oxygen? STEP 1: Convert to moles. 25.9 g N x 1 mol N = 1.85 mol N 14.0 g N 74.1 g O x 1 mol O = 4.63 mol O 16.0 g O

  17. STEP 2: Determine the lowest whole-number ratio 1.85 mol N = 1 mol N 1.85 4.63 mol O = 2.50 mol O 1.85 STEP 3: Convert any fractions to whole numbers. N2O5

  18. Calculating Molecular Formulas • MOLECULAR FORMULA:Multiple of the empirical formula • Calculate the molecular formula of the compound whose molar mass is 60.0 g and empirical formula is CH4N. www.brainybetty.com

  19. Empirical formula mass = 30.0 g/mol (efm) Molar mass = molecular formula efm 60.0 g = 2 C2H8N2 30.0 g www.brainybetty.com

More Related