1 / 29

Regents Chemistry

Regents Chemistry. Topic III. Stoichiometry. What’s a Mole???. One mole of ANY specified entity contains 6.022 x 10 23 of that entity. For example:. One mole of donuts contains 6.022 x 10 23 donuts One mole of H 2 O contains 6.022 x 10 23 molecules

didier
Download Presentation

Regents Chemistry

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. Regents Chemistry Topic III Stoichiometry

  2. What’s a Mole??? One mole of ANY specified entity contains 6.022 x 1023 of that entity. For example: • One mole of donuts contains 6.022 x 1023 donuts • One mole of H2O contains 6.022 x 1023 molecules • One mole of nails contains 6.022 x 1023 nails • One mole of Fe contains 6.022 x 1023 atoms • One mole of dogs contains 6.022 x 1023 dogs • One mole of electrons contains 6.022 x 1023 electrons

  3. (Covalently bonded)

  4. These are Formula units!

  5. How can we measure a mole? • A mole = 6.022 x 1023 particles • Could be a mole of an ionic compound • contains 6.022 x 1023 formula units (made of ions) • Could be a mole of a molecular compound • contains 6.022 x 1023 molecules (made of elements) • A mole of an element = the average atomic mass listed on the periodic table • A mole of a compound = total mass of the moles in the compound

  6. Finding the Mass of a Mole of a Compound

  7. Example #1

  8. Example #2

  9. Summary • Formula mass - mass of the smallest unit of an ionic compound; sum of atomic masses in amus • Gram Formula Mass - same as formula mass except in grams • Molecular Mass – same as FM except for used for molecular substances • Mole – 6.022 x 1023 particles of anything! Just know it is also the GFM of any substance

  10. Regents Chemistry • Mass, Mole and Particle conversions

  11. The Conversion Flowchart Mass of compound Number of Particles multiply by molar mass multiply by 6.02 x 1023 divide by molar mass Mole divide by 6.02 x 1023 divide by 22.4 liters multiply by 22.4 liters Liters of Gas

  12. Practice mole to mass • How many grams are in 2 moles of CuCl2? • How many grams are in 3.5 moles of H2O 2 moles CuCl2 x 134g per mole = 268 g 3.5 moles H2O x 18g per mole = 63 g

  13. Mass to Mole • How many moles of NO are in 67.0g of NO? • How many moles of KCl are in 125.0g of KCl? 67.0 g NO / 30.0 g per mole = 2.2 moles NO 125.0 g KCl / 74.5 g per mole = 1.68 moles KCl

  14. Regents Chemistry • Finding Percent Composition

  15. What is Percent Composition? • Formulas represent the composition of a substance • If we use the subscripts and atomic masses of the elements, we can find the percent by mass of each element in a substance • Essentially, Percent Composition finds how much of each element is in a substance

  16. How do we do this???? • 1. We can add up the total molar mass of all elements involved in the substance • 2. We next simply divide the total of the element in question by the total molar mass and multiply by 100%

  17. Example #1 • Find the percent composition (in grams) of oxygen in potassium chlorate 2. Divide and multiply by 100% 1. Find the molar mass KClO3 K - 1 mole x 39.1 grams = 39.1 g Cl - 1 mole x 35.5 grams = 35.5 g O - 3 moles x 16.0 grams = 48.0 g %O = 48.0 g x 100% 122.6 g Molar mass = 122.6 g %O = 39.2%

  18. Moles and molecules/formula units • Moles - measured in grams • molecules / formula units - measured in amu (atomic mass units) • So… grams make up moles of a substance • and amu (atomic mass units) make up individual molecules/formula units • Use the same numbers from the PT!

  19. It’s the same process to find the % of amu in a 1 molecule or formula unit! • Find the percent composition (in amu) of oxygen in potassium chlorate 2. Divide and multiply by 100% 1. Find the mass in amu KClO3 K - 1 atom x 39.1 amu = 39.1 amu Cl - 1 atom x 35.5 amu = 35.5 amu O - 3 atoms x 16.0 amu = 48.0 amu %O = 48.0 amu x 100% 122.6 amu Formula mass = 122.6 amu %O = 39.2%

  20. Example #2 • Find the percent composition (in amu) of water in sodium carbonate crystals Na2CO3 • 10H2O 3. Divide %H2O = 180.0 amu x 100% --------------- 286.0 amu %H2O = 62.9% 1. Formula Mass = 286.0 amu 2. Total formula mass of H2O = 180.0 amu worksheet

  21. Regents Chemistry • Mole Relations in Balanced Equations

  22. RECAP • The Law of Conservation of Mass tells us: • Moles (and atoms) in equations must be balanced • Since moles (and atoms) have mass, mass is also balanced (we did this by finding missing mass) • So we have relationship between reactants and products • Thus if we change the moles of reactants (or number of atoms) we change the moles /# of atoms of products..HOW?

  23. Mole Relations • Balanced Chemical Equation: 2C2H6 + 7O2 4CO2 + 6H2O MolesC2H6 MolesO2 MolesCO2 MolesH2O 2 7 4 6 4 14 8 12 1 3.5 2 3

  24. Sample Problem • How many moles of water will be produced from the complete combustion of 3.0 mol of ethane? 2C2H6 + 7O2 4CO2 + 6H2O moles ethane:moles water = 2:6 3.0 mole C2H6 = x 2.0 mole C2H6 6 mole H2O x = 9.0 mole H2O

  25. Finding the Mass Produced • Sample Problem Cont.. • How many grams of water are produced 9.0 mole H2O produced ( ) #g H2O = 9.0 mole H2O 18.0g H2O = 162 g H2O 1 mole H2O

  26. Sample Problem #2 • How many moles of iron (III) oxide are produced from the combination of 6 moles of Fe ? How many grams? 4Fe + 3O2 2Fe2O3 6 mole Fe=x mole Fe2O3 4 mole Fe 2 mole Fe2O3 x= 3 mole Fe2O3 equals 480g Fe2O3

More Related