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What is the Mole?

What is the Mole?. Hint: Its not a small mammal…. The Mole in Chemistry. The mole is a unit of measurement in chemistry. The mole is similar to other counting units such as 12 eggs equals 1 dozen. One mole of any substance contains 6.02x10^23 number of particles. (Avogadro's Number)

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What is the Mole?

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  1. What is the Mole? Hint: Its not a small mammal…

  2. The Mole in Chemistry • The mole is a unit of measurement in chemistry. • The mole is similar to other counting units such as 12 eggs equals 1 dozen. • One mole of any substance contains 6.02x10^23 number of particles. (Avogadro's Number) • Therefore, one mole of eggs would have 602000000000000000000000 eggs. • The mole is a great way to count matter without using really big numbers. • This is important for chemistry because there are millions of particles in small amounts of substances

  3. The Mole in Chemistry (Cont.) • The mole is a great way to count matter without using really big numbers. • This is important for chemistry because there are millions of particles in small amounts of substances • Just 18 mL (or grams) of water contains 6.02x10^23 molecules of water • This presentation will help to explain how we can find out how many moles and molecules are in a given amount of a substance.

  4. A Mole of Carbon There are 12 grams in one mole of carbon. All of the other elements mole number is relative to that of carbons. Amazingly, there are 6.02x10^23 atoms in each of the samples above.

  5. How to Calculate the Mole • A sample of 12 grams of carbon is equal to one mole. • The amount of moles in a substance can be determined using that substance’s molar mass. • The molar mass is the amount of grams in one mole of a substance. • The molar mass is the average atomic mass for a substance. • Ex. Carbon has an atomic mass of 12 amu so its molar mass is 12 g/mol

  6. Molar Mass • The molar mass of an atom, molecule, or compound is the number of grams in one mole of the substance. • Molar Mass = Grams/mole • Ex. Molar Mass of pure Sodium (Na) • Find Sodium on the Periodic Table • The molar mass is equal to the atomic mass • Therefore, the molar mass is 22.99 or 23.0 grams

  7. Calculating Molar Mass for Compounds • For compounds, the molar mass is the combined total of all the atomic masses for each atom in the compound. • Ex. C6H12O6 • There are 6 carbons, 12 hydrogen, and 6 oxygen • Carbon has an atomic mass of 12, so we multiply 12 by 6 for a total of 72. • We do the same for hydrogen and oxygen and add them all together for the molar mass. • C: 6(12) = 72, H: 12(1) = 12, O: 6(16) = 96 • So, 72+12+96 = 180 grams/mole

  8. You Try! • What is the molar mass of NH3? • 14 g • 17 g • 4 g • 25 g Use the Periodic Table

  9. Try Again • Use this other example of how to calculate molar mass. • Try Again

  10. Correct!!! • Good Answer! Now learn about mole conversions.

  11. Mole Conversions • Grams have to be converted to moles before converting to number of particles. • Grams x 1mol/molar mass = Moles • Moles x 6.02x10^23/1mol = Particles

  12. Calculating the Moles in a Given Substance • Suppose you were given a graduated cylinder with 18 mL of water in it and you were told to find the number of moles. (Hint: 18 mL of water is equal to 18 grams of water) • First, we need to find the molar mass for water (H2O) using the average (or relative) atomic masses on the periodic table. • 2 H @ 1 g each = 2 g • 1 O @ 16 g = 16 g • 2 g + 16 g = 18 g of water in 1 mole • Second, we set up a conversion factor to convert the grams of water to moles. • 18 grams H2O x 1 mole H2O/18 grams H2O (the grams cancel and we are left with moles) • = 1 mole of water

  13. Calculating Number of Particles from Moles • You can convert moles to the number of particles of a substance. • Take the number of moles and multiply it by Avogadro’s Number (6.02x10^23) • For example, we found that 18 grams of water is equal to 1 mole. • 1mole water x 6.02x10^23 particles/mole = 6.02x10^23 particles

  14. Let’s Try That Again! • Suppose that you have 117 grams of table salt (NaCl). How many particles of salt are present? • First, calculate the molar mass (using the average atomic masses on the Periodic Table) • 1 Na @ 23g = 23g • 1 Cl @ 23.5g = 35.5g • 23g + 35.5g = 58.5g • Second, convert grams to moles • 117g NaCl x 1 mole NaCl/58.5g NaCl = 2 moles NaCl (the grams cancel and you are left with moles) • Third, convert moles to particles (using Avogadro's Number) • 2 mole NaCl x 6.02x10^23 particles NaCl/1 mole NaCl = 1.2x10^24 particles NaCl

  15. Now You Try! • If you were given a 78g sample of LiF, how many moles would be present in the sample? Use the Periodic Table. A. 1 mole B. 2 moles C. 3 moles D. 4 moles

  16. Calculating Molar Masses Using the Periodic Table • You can find the molar mass of an element by looking at its atomic mass. Here it is located directly under the element symbol and is 107.87. • To find the atomic mass for a compound you just have to count the number of each element and find the atomic mass for each then add them together. • For example, AgO3 is • 1 Ag @ 107.87g • 3 O @ 16g = 16x3 = 48g • 107.87g + 48g = 155.87g • So, there are 155.87g in one mole of AgO3

  17. Not Quite • Review the example problem and try again.

  18. Correct!!! • Great Job!

  19. Another Example Problem • How many moles are in 12 grams of NH3? • 1.0 • 2.5 • .71 • 1.8 Need the Periodic Table?

  20. Incorrect • Please try again.

  21. Yup!!! • Good Answer. Now try to convert moles to particles.

  22. Try This One • How many atoms are present in 2.5 moles of pure sodium? A. 1.5x10^24 B. 1.2x10^23 C. 57.5 D. 135.8

  23. Nope… • Try Again!

  24. You’re Right!!! • Good Work!

  25. Final Assessment • How many particles (molecules) of glucose (C6H12O6) are present in a 270 gram sample? • 1.5 • 9.03x10^23 • 6.02x10^23 • 2

  26. Not Quite • Remember it’s a two step process. You have to convert grams to moles and then moles to particles. • Try Again

  27. Great Job! • You have learned about the mole and mole conversions!

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