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Bell Ringer 3-31-14

Bell Ringer 3-31-14. 4Al + 3O 2 → 2Al 2 O 3 For every ____ atoms of Al that react, there are ____ formula units of Al 2 O 3 produced. Determine which numbers go in the blanks, then write the statement above as a ratio. 4 Al + 3 O 2 → 2 Al 2 O 3

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Bell Ringer 3-31-14

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  1. Bell Ringer 3-31-14 4Al + 3O2 → 2Al2O3 • For every ____ atoms of Al that react, there are ____ formula units of Al2O3 produced. • Determine which numbers go in the blanks, then write the statement above as a ratio

  2. 4Al + 3O2 → 2Al2O3 For every 4 atoms of Al that react, there are 2 formula units of Al2O3 produced. Write the statement above as a ratio 4 atoms Al__ 2form u. Al2O3

  3. Ratios in Chemical Equations 3-31-14

  4. In a balanced chemical equation: • The coefficients tell you the relative amounts of each reactant and product • Use the coefficients as the numbers in your ratio • So far, we have learned that units may be atoms, molecules, or formula units

  5. Atoms – elements (not diatomic, ex. Al, C) • Molecules – diatomic elements and covalent compounds (made of nonmetals, ex. O2, H2O) • Formula Units - ionic compounds (made of metals + nonmetals, ex. NaCl, LiO2)

  6. Visualizing at the Atomic Level 4Al + 3O2 → 2Al2O3 Looks like this: +→

  7. Can we actually count atoms? • No! We cannot see individual atoms, molecules, or formula units So scientists came up with a new unit (a mole)that is sooooooooooo big that you cansee a mole of atoms (or molecules, or formula units)

  8. The Mole An amount of particles of a pure substance. It is a very, very, very, very, very, very, very, very LARGE number

  9. MOLE = 6.02 x 10 23

  10. Review: Scientific Notation 6.02 x 10 23 = 602,000,000,000,000,000,000,000 Other Scientific Notation Problems: 4.267 x 10 8= 426,700,000 = 4.267 x 10 -8 = 426,700,000 4.267 x 10 8 .00000004267

  11. Mole is a word that is used to indicate a number. What are some other words we use to tell how many of something we have? • PAIR= • DOZEN = • GROSS = 2 12 144

  12. What is a mole? 602,000,000,000,000,000,000,000 = six hundred and two sextillion = 6.02 x 1023

  13. Why use a mole? • Scientists use the mole, and the concept of molar mass to determine how much of each reactant to use, and to predict how much of each product they will get. • Molar mass is the mass of one mole of a substance (more about that later this week)

  14. Just how big is a mole? • 6.02 X 1023 Watermelon Seeds: Would be found inside a melon slightly larger than the moon. • 6.02 X 1023Donut Holes: Would cover the earth and be 5 miles (8 km) deep. • 6.02 X 1023Pennies: Would make at least 7 stacks that would reach the moon. • 6.02 X 1023Grains of Sand: Would be more than all of the sand on Chicago’s Beaches.

  15. How many atoms are in a mole of hydrogen atoms? 6.02 x 10 23

  16. How many molecules are in a mole of water molecules? 6.02 x 10 23

  17. How many marshmallows are in a mole of marshmallows? 6.02 x 10 23

  18. 1 EXAMPLE: Using moles in a ratio: C3H8+ 5O2→ 3CO2 + 4H2O For every __ _ mole of C3H8reacted, there are ____ moles of CO2produced. There are __ moles of H2O produced for every _____ moles of O2 that react. Write the ratios: 1 mole C3H8 4 moles H2O 3 molesCO2 5 moles O2 1 3 4 5

  19. What is a mole? 602,000,000,000,000,000,000,000 = six hundred and two sextillion = 6.02 x 1023

  20. More Practice: 2HgO → 2Hg + O2 What is the ratio of moles of HgO to moles of Hg? 2 moles HgO or 1 mole HgO 2 moles Hg 1 mole Hg So if you react 7 moles of HgO, how many moles of Hg are produced?

  21. What is the mass of one mole of: look at your periodic table, Write our answer in your notes, then raise your hand S C Hg Cu Fe 3.2

  22. If you wanted to find the mass of the whole class, what would you have to do? • Find the mass of each student (put them on a scale) • Add the mass of each student together • = total mass

  23. If you wanted to find the mass a whole compound, what would you have to do? • Find the mass of each atom (look at the periodic table) • Add the mass of each atom together • = total mass

  24. S-1 32.07 amu O-2 + 2 x 15.99 amu SO2 SO2 64.05 amu Molar mass(or molecular weight) is the total amount of the atomic masses in a molecule. Unit = u • Steps: • 1. Determine how many atoms are there of each element? • 2. What are the masses? • 3. Add all the masses For any molecule molecular mass (u) = molar mass (grams) 1 molecule SO2 = 64.05 amu 1 mole SO2 = 64.05 g SO2 3.3

  25. Example 1: show your work Find the Molecular Mass of H2O H - 2 O- 1 X 1.008 = 2.016 + X 15.99 = 15.99 18.006 g

  26. Example 1: show your work Find the Molecular Mass of 2 moles of H2O H - 2 O- 1 X 1.008 = 2.016 = 36.012 + = X 15.99 = 15.99 1 36.012 g of H2O 18.006 g 1 mol of H2O 18.006 g of H2O 2 mol of H2O 18.006 g of H2O = 1 mol of H2O 2 mol of H2O

  27. Example 3: show your work Find the Molecular Mass of CaCl2 Ca - 1 Cl - 2 X 40.08 = 40.08 + X 35.45 = 70.9 110.98 g

  28. Example 4: show your work Find the Molecular Mass of 4 moles of CaCl2 = 443.92 = 1 443.92 g of CaCl2 1 mol of CaCl2 110.98 g of CaCl2 4 mol of CaCl2 110.98 g of CaCl2 = 1 mol of CaCl2 4 mol of CaCl2

  29. Honors Exit Slip: Half sheet, 6 Formative Assessment points (Grade category 15%) 1. How many atoms are there in a mole of helium? 2. How many molecules are there in a mole of methane? 3. What is the mass of 1 mole of magnesium? 4. What is the mass of 1 mole of carbon dioxide? What is the mass of 2 moles of Carbon Dioxide? 5. What is the mass of one mole of O2? What is the mass of 2 moles of O2? 6. What is the mass of one mole of LiCN? What is the mass of 5 moles of LiCN?

  30. Exit Slip: Half sheet, 6 Formative Assessment points (Grade category 15%) 1. How many atoms are there in a mole of helium? 2. How many molecules are there in a mole of methane? 3. What is the mass of 1 mole of magnesium? 4. What is the mass of 1 mole of carbon dioxide? 5. What is the mass of one mole of O2? 6. What is the mass of one mole of LiCN?

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