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Meet the Mole.

Meet the Mole. Moles. The mole is a unit of measurement. The unit can be defined in multiple ways. (We’ll learn 3 today.) In its simplest terms, it represents a specific number. Dozen = what number? Pair = what number? Baker’s dozen = what number? Mole = 6.02 x 10 23

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Meet the Mole.

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  1. Meet the Mole.

  2. Moles • The mole is a unit of measurement. • The unit can be defined in multiple ways. (We’ll learn 3 today.) • In its simplest terms, it represents a specific number. • Dozen = what number? • Pair = what number? • Baker’s dozen = what number? • Mole = 6.02 x 1023 • Atoms are SUBmicroscopic. In order to have an amount large enough with which to really interact, we need quite a few atoms.

  3. Avogadro’s Number • 6.02x1023 • My pet mole is named Avogadro.

  4. Defining the Mole • Counting • Weighing • Amount of Space Needed

  5. Molar mass Example 6.5 • Some questions simply test your understanding of the definitions. • Calculate the molar mass of sulfur dioxide, a gas produced when sulfur-containing fuels are burned. • SO2 • S = 32.07 g • O = 2(16.00 g) • Total = 64.07 g/mol • Can also be expressed as 1 mol SO2 = 64.07 g

  6. Molar Mass Practice Problem 6.5 • Polyvinyl chloride, called PVC, which is widely used for floor coverings (“vinyl”) as well as for plastic pipes in plumbing systems, is made form a molecule with the formula C2H3Cl. Calculate the molar mass of this substance. • 62.49 g/mol

  7. Unit Conversion Example 6.3 • Most questions will require you to apply the definitions to convert from one unit to another. • Aluminum (Al), a metal with a high strength-to-weight ratio and a high resistance to corrosion, is often used for structures such as high-quality bicycle frames. Compute both the number of moles in a 10.0-g sample of aluminum.

  8. Unit Conversion Example 6.4 • A silicon chip used in an integrated circuit of a computer has a mass of 5.68 mg. How many silicon (Si) atoms are present in this chip? The average atomic mass for silicon is 28.09 amu.

  9. Unit Conversion Example • During cellular respiration, a cell releases 0.25 mol of O2 gas. What volume is needed to hold this gas?

  10. Partner PracticeBack together with 10 min left in class. 10-2 Practice Problems (1-3, 12-14, 17, 18, 23-25)

  11. Calculate the number of formula units in a 45.0 gram sample of FeO. Exit Question

  12. Problem-Based Learning Activity Exit Question Groups

  13. HIGHER LEVEL APPLICATIONS OF MOLE • Let’s make sure that we all understand how the particle vocabulary can complicate a problem. • Consider: Calculate the number of oxygen atoms in 3.5 g aluminum sulfate. • A few examples in your practice packet.

  14. Choose a partner. Work is due at the end of the period. MOLE THINK TAC TOE

  15. Percent Composition • The relative amounts of each element in a compound are expressed in percent composition. • AKA: percent by mass of each element • % of element = grams of element X 100 grams of compound

  16. Percent Composition Example 6.9 • Carvone is a substance that occurs in two forms, both of which have the same molecular formula (C10H14O) and molar mass. One type of carvone give caraway seeds their characteristic smell; the other is responsible for the smell of spearmint oil. Compute the mass percent of each element in carvone.

  17. Connecting Moles & Mass % to Chemical Formulas • Mass % is easily related to chemical formulas • The relationship of moles to chemical formulas requires a little more thought. • First, let’s learn two new vocabulary words.

  18. Type of Chemical Formula: Empirical Formula • Empirical formula: lowest whole number ratio of the atoms of the elements in a compound • Ionic compounds are criss-crossed and then reduced. Ionic compound formulas are nearly always empirical formulas. • Covalent compounds are not always reduced formulas. (Ex. C6H12O6) • Therefore, an empirical formula doesn’t have to be the same as the actual molecularformula of the compound.

  19. Empirical Formula • CH2O • Calculate the mass percent of each element. • C = 40% • H = 6.7% • O = 53.3% • Isn’t this the reduced formula for: C3H6O3, C4H8O4, C5H10O5, & C6H12O6 • The mass percent of each of these compounds is the same.

  20. Type of Chemical Formula: Molecular Formula • Molecular formula: actual formula for the compound which gives the composition of the molecule • Glucose shares an empirical formula with many compounds, but it has its molecular formula all to itself. • 6(CH2O) = glucose

  21. Applying the vocabulary • When an unknown compound is found, instruments can tell scientists the mass percent composition of the compound. • Calculations are required to convert that series of percentages into a chemical formula. • We start by converting to the empirical formula. • Situation: A white solid has been found on the floor of a government mailroom. Is it dangerous? • Step 1: Mass spectrometer analysis • 40.9 % Carbon • 4.58% Hydrogen • 54.5% Oxygen • Molar mass of 180 grams/mole • Step 2: Convert % to formula with simple calculations

  22. Calculating Empirical Formula Use a simple rhyme! • % to gram • Gram to mole • Divide by the smallest • Multiply ‘til whole. • Situation: A white solid has been found on the floor of a government mailroom. Is it dangerous? • Mass spectrometer analysis • 40.9 % Carbon • 4.58% Hydrogen • 54.5% Oxygen • Molar mass of 180 grams/mole

  23. Empirical Formula Example 6.11 • An oxide of aluminum is formed by the reaction of 4.151 g of aluminum with 3.692 g of oxygen. Calculate the empirical formula for this compound. • % to gram = IS DONE FOR YOU • Gram to mole = dimensional analysis • Let’s carry out the calculation on the board.

  24. Empirical formula Example 6.13 • A sample of lead arsenate, an insecticide used against the potato beetle, contains 1.3813 g of lead, 0.00672 g of hydrogen, 0.4995 g of arsenic, and 0.4267 g of oxygen. Calculate the empirical formula for lead arsenate.

  25. Empirical Formula Example 6.14 • The most common form of nylon is 63.68% carbon, 12.38% nitrogen, 9.80% hydrogen, and 14.4% oxygen. Calculate the empirical formula for nylon.

  26. Calculating Molecular Formula • Molecular Formula= n(empirical formula) (Remember 6(CH2O) = glucose) • We know how to calculate the empirical formula, but how do we know what number to multiply it by? n= actual formula mass/molar mass of empirical

  27. Molecular formula Example 6.15 • A white powder is analyzed and found to have an empirical formula of P2O5. The compound has a molar mass of 283.88 g/mol. What is the compound’s molecular formula?

  28. Molecular formula Practice Problem 6.15 • A compound used as an additive for gasoline to help percent engine knock shows the following percentage composition: • 71.65% Cl • 24.27% C • 4.07% H • The molar mass is known to be 98.96 g. Determine the empirical formula and the molecular formula for this compound.

  29. Problem-based learningday 1: forensic chemistday 2: Assistant medical examiner Mole Airlines

  30. The final product in protein metabolism is urea. Urea contains 20.00% C, 6.73% H, 46.65% N, and 26.64% O. The molar mass of urea is 60.07g/mol. Calculate the empirical formula and molecular formula. Warm up for Quiz

  31. Problem-based learningday 1: forensic chemistday 2: Assistant medical examiner Mole Airlines

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