1 / 44

As you come in,

As you come in,. The Materials: Pick up a packet and assessment plan. Paper , pencil, scientific calculator, periodic table The Plan: Learn about 3 definitions of a mole Solve dimensional analysis problems HOMEWORK: See your calendar!. Meet the Mole. Moles.

cullen
Download Presentation

As you come in,

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. As you come in, • The Materials: • Pick up a packet and assessment plan. • Paper, pencil, scientific calculator, periodic table • The Plan: • Learn about 3 definitions of a mole • Solve dimensional analysis problems • HOMEWORK: • See your calendar!

  2. Meet the Mole.

  3. Moles • The mole is a unit of measurement used in chemistry. • 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 = 6.022 x 1023

  4. Mole = 6.022x1023 things • Just like a dozen means 12 of anything... 6.022x1023 of anything equals of mole. • Consider the size of 6.022x1023. Is it large or small? • Would you commonly use 6.022x1023 with large things or small things?

  5. Atoms, Elements, & Compounds • In chemistry, we are often dealing with VERY SMALL things. • Atoms are SUBmicroscopic. In order to have an amount large enough with which to really interact, we need quite a few atoms. 6.022x1023 is the number that Amadeo Avogadro chose in his lab using carbon.

  6. Avogadro’s Number • 6.022x1023 • My pet mole is named Avogadro.

  7. Defining the Mole • Counting • Weighing • Amount of Space Needed • Let’s represent our 3 mole definitions in a graphic organizer.

  8. Moles & Mass of Compounds • A compound is a collection of atoms. • To calculate the mass of one mole of a compound, you’d need to add up the mass of all the atoms. This is called the MOLAR MASS. • Example: 1 mole CH4 = ______ g CH4 • 1 C = 12.011 g C • 4 H = 4(1.0079 g H) • Total = 16.04 g/mol

  9. iRespond Question Fill-In F Example 6.5 Calculate the molar mass of sulfur dioxide, a gas produced when sulfur-containing fuels are burned. Record your answer to TWO decimal places. A.) 64.07;64.10;64.1 B.) C.) D.) E.)

  10. Example 6.5 • 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

  11. iRespond Question Fill-In F Practice Problems 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. Record the answer to TWO decimal places. A.) 62.49;62.50;62.5 B.) C.) D.) E.)

  12. Practice Problems 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

  13. Learning to Use the Mole Map • Using the Mole Concept to Calculate • Page 182-7 • EX 6.3, EX 6.4, EX. 6.6

  14. Example 6.3 • 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 of atoms and the number of atoms in a 10.0-g sample of aluminum. • How many calculations is this prompt asking me to carry out?

  15. Example 6.3 (Guided) • 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 of atoms and the number of atoms in a 10.0-g sample of aluminum. • Concentrate on one calculation at a time

  16. Example 6.4 (INDEPENDENT) iRespond Question Multiple Choice F 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. A.) 3.36X10-25 B.) 1.22X1023 C.) 1.22X1020 D.) none of these E.)

  17. Example 6.6 (GUIDED) • Calcium carbonate, CaCO3 (also called calcite), is the principal mineral found in limestone, marble, chalk, pearls, and the shells of marine animals. • Calculate the molar mass of calcium carbonate. • A certain sample of calcium carbonate contains 4.86 mol. What is the mass in grams of this sample?

  18. Practice Problem 6.6 iRespond Question Multiple Choice F Calculate the molar mass for sodium sulfate, Na2SO4. A sample of sodium sulfate with a mass of 300.0 g represents what number of moles of sodium sulfate? A.) 2.112 B.) 42,600 C.) 2.520 D.) none of these E.)

  19. Molar Volume • If converting between the units of moles and liters of a gas, what conversion factor is needed? • 1 mole = ________________ • 1 mole = 22.4 Liters • Example: During cellular respiration, a cell releases 2.1 mol of O2 gas. What volume is needed to hold that gas?

  20. Example 6.7 (GUIDED) • Juglone, a dye known for centuries, is produced from the husks of black walnuts. The formula for juglone is C10H6O3. • A sample of 1.56 g of pure juglone was extracted from black walnut husks. How many moles of juglone does this sample represent? • How many atoms of carbon are present in the sample?

  21. Partner Practice • On a clean sheet of paper, show your work for 10-2 Practice Problems (1-3, 12-14, 17, 18, 23-25).

  22. Chalk lab Example (Guided) • Last week, you created a poster using chalk. • How many grams of chalk did you use on the poster? • How many moles of chalk did you use? • How many formula units of chalk did you use? • How many atoms of Ca did you use? • How many atoms of C did you use? • How many atoms of O did you use?

  23. Mole/Particle Practice Problems • I marked mistakes on your papers, but I did not correct them. • Correct and complete 1-8 tonight for homework. • Let’s solve 9 and 10 together now.

  24. 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

  25. Example 6.9 (GUIDED) • 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.

  26. Percent by Mass Worksheet • Individually, calculate the mass percents of the first three compounds on the worksheet. • Let’s check your work.

  27. 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...

  28. 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. • Empirical formula doesn’t have to be the same as the actual molecular formula of the compound. • Remember, “molecule” means covalent compound. Covalent compounds weren’t always in a reduced form.

  29. 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 • Row 1: Calculate the mass percent of C3H6O3. • Row 2: Calculate the mass percent of C4H8O4. • Row 3: Calculate the mass percent of C5H10O5. • Row 4: Calculate the mass percent of C6H12O6. • The percentages (ratio) of the elements is the same with all of these formulas because they share the same reduced form.

  30. 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 • C6H12O6

  31. Calculating Empirical Formulas • 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.

  32. What is she talking about? • White powder found in the hallway • Mass spectroscopy instrument used to analyze the unknown powder • Data from the instrument: • 40.9 % Carbon • 4.58% Hydrogen • 54.5% Oxygen • Molar mass of 180 grams/mole • Use these %s, formula knowledge, & mole knowledge to figure out the chemical formula of the powder

  33. Calculating Empirical Formula • Use a simple rhyme! • % to gram • Gram to mole • Divide by the smallest • Multiply ‘til whole.

  34. 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.

  35. 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.

  36. 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.

  37. 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= molecular formula mass/molar mass of empirical

  38. 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?

  39. 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.

  40. Individual Practice • Page 208 4-6

  41. You may not be practicing enough… • On a clean sheet of paper, work the following problems individually: • Calculate the number of oxygen atoms in 3.5 g aluminum sulfate. • Calculate the number of molecules of O2 gas in 2.5 L of O2. • Calculate the number of grams of iron that contain the same number of atoms as 2.24 g of cobalt. (pg 214 #57) • Quiz answers are coming.

  42. Empirical/Molecular Formula • 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.

  43. Hydrate Lab Details • You’ll have to READ (not skim) the lab to be successful. • Steps 1-5 are probably unnecessary. • Steps 6-11 are vital. Substitute hot plate for Bunsen burner. • Notice the “Observations and Data” area on the back. You’ll need those measurements. • The calculations are described to you in each question. Just follow the directions. • You’ll need to answer the “Questions for Discussion,” too.

  44. Calculations hints • Subtract. • % water lost =[water lost/hydrate mass]100 • % water in hydrate = [5(water molar mass)/total molar mass] 100 • Subtract. %water in hydrate - %water lost from your hydrate • % error = [#4 answer/#3 answer]100

More Related