1 / 26

The Mole Concept

The Mole Concept. Review: Avogadro’s Number. Avogadro’s Number (symbol N) is named in honor of Italian chemist Amadeo Avogadro It tells us the number of atoms in 1 mole of a substance The value of Avogadro’s number is 6.02x10 23. Review: Mole.

lionel
Télécharger la présentation

The Mole Concept

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. The Mole Concept

  2. Review: Avogadro’s Number • Avogadro’s Number (symbol N) is named in honor of Italian chemist Amadeo Avogadro • It tells us the number of atoms in 1 mole of a substance • The value of Avogadro’s number is 6.02x1023

  3. Review: Mole • The mole (symbol mol) is a unit of measure for an amount of a chemical substance • We define it as the amount of substance that contains Avogadro’s number of particles • The individual particles can be atoms, molecules, formula units, etc.

  4. Review: Mole • 1 Mole= Avogadro’s number (N) • Avogadro’s number =6.02x1023particles • 1 Mole=6.02x1023 particles

  5. Mole Analogies • If 6.02x1023atoms of hydrogen were laid side by side, the total length would be long enough to circle the Earth 1,000,000 times • The mass of 6.02x1023 Olympic shot-put balls would equal the mass of the Earth • The volume of 6.02x1023softballs would equal the volume of the Earth • Extra Credit Question: If $6.02x1023 earns 5% interest per year, how many dollars does the account earn every nanosecond? (must show all work to receive credit)

  6. Mole Calculations: Nmoles • We can convert between the number of particles and the number of moles. • Example: • How many moles of Iodine are in 2.5x1023 molecules of I2?

  7. Mole Calculations: molesN • We can convert between the number of moles and the number of particles. • Example: • How many molecules of chlorine are in 0.250 moles of the gas?

  8. Molar Mass • Molar mass is the mass of 1 mole of a substance • For elements the molar mass is equal to its atomic mass, which we find on the periodic table • For compounds the molar mass is equal to the sum of the individual elements that make it up

  9. Molar mass examples • Find the molar mass of the following substances: • Silver metal • Magnesium nitrate • NH3 • Manganese metal • Strontium acetate • Sulfur hexaflouride

  10. Mole Calculations: gramsmol • We can convert between the mass of a substance and the number of moles. • Example • How many moles are in 87.8g of Pb?

  11. Mole Calculations: molgrams • We can convert between the mass of a substance and the number of moles. • Example • How many grams are in 3.2 moles of (NH4)3PO4 ?

  12. Mole Calculations: g  N • We can also convert between mass and the number of particles • Example: • How many molecules are present in 1.470g of O2 gas?

  13. Mole Calculations: g  N • We can also convert between the number of particles and mass • Example: • What is the mass in grams of 2.01x1022 atoms of sulfur?

  14. Percent composition • Percent composition is a list of the mass percent of each element in a compound • Before we continue we need to discuss what percentages are. • Percent expresses the amount of a single quantity compared to the entire sample

  15. Calculating % composition • Calculate the percent composition for each element in H2O

  16. Calculating % composition • Calculate the percent composition for each element in Trinitrotoluene (TNT), C7H5(NO2)3

  17. Empirical Formula • In the late 1700’s chemists were very interested in chemical reactions, especially those with oxygen. • This was because chemists could determine the formula of a compound after the reaction through the use of empirical formulas • Empirical formulas are the simplest whole number ratio of atoms in an element

  18. Empirical Formula

  19. Empirical Formula • Glycine is an amino acid found in protein. An analysis of glycine gave the following data: 32.0% carbon, 6.7 % hydrogen, 18.7% nitrogen, and 42.6% oxygen. Calculate the empirical formula for the amino acid. (Assume 100g sample)

  20. Empirical Formula • Calculate the empirical formula for caffeine. An analysis of caffeine gave the following data: 49.5% carbon, 5.15 % hydrogen, 28.9% nitrogen, and 16.5% oxygen. (Assume 100g sample)

  21. Molecular Formulas • Molecular formulas indicate the actual numbers of atoms of each element in one molecule • Benzene, styrene and acetylene, while very different substance with very different properties, all have the same empirical formula CH. • Because they are different compounds they must have different formulas and therefore different molar masses.

  22. Calculating molecular formulas • Acetylene: 26 g/mole

  23. Calculating molecular formulas • Benzene: 78 g/mole

  24. Calculating molecular formulas • Styrene: 104 g/mole

  25. Calculating molecular formulas • The empirical formula for fructose is CH2O. If the molar mass of fructose is 180g/mol, find the molecular formula of fructose.

  26. Calculating molecular formulas • Ethylene dibromide was used as a grain pesticide until it was banned in 1983. • A. Find the empirical formula if the percent composition is 12.7% C, 2.1% H and 85.1% Br. • B. If the molar mass is 180g/mol, find the molecular formula of ethylene dibromide.

More Related