Presentation on theme: " The Materials: Pick up a packet and assessment plan. Paper, pencil, scientific calculator, periodic table The Plan: Learn about 3 definitions."— Presentation transcript:
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!
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 10 23
Just like a dozen means 12 of anything... 6.022x10 23 of anything equals of mole. Consider the size of 6.022x10 23. Is it large or small? Would you commonly use 6.022x10 23 with large things or small things?
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. 6.022x10 23 is the number that Amadeo Avogadro chose in his lab using carbon.
Counting Weighing Amount of Space Needed Let’s represent our 3 mole definitions in a graphic organizer.
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 CH 4 = ______ g CH 4 1 C = 12.011 g C 4 H = 4(1.0079 g H) Total = 16.04 g/mol
Calculate the molar mass of sulfur dioxide, a gas produced when sulfur- containing fuels are burned. SO 2 S = 32.07 g O = 2(16.00 g) Total = 64.07 g/mol Can also be expressed as 1 mol SO 2 = 64.07 g
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 C 2 H 3 CL. CALCULATE THE MOLAR MASS OF THIS SUBSTANCE. RECORD THE ANSWER TO TWO DECIMAL PLACES.
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 C 2 H 3 Cl. Calculate the molar mass of this substance. 62.49 g/mol
Using the Mole Concept to Calculate Page 182-7 EX 6.3, EX 6.4, EX. 6.6
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?
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
A.) 3.36X10 -25 B.) 1.22X10 23 C.) 1.22X10 20 D.) none of these
Calcium carbonate, CaCO 3 (also called calcite), is the principal mineral found in limestone, marble, chalk, pearls, and the shells of marine animals. a) Calculate the molar mass of calcium carbonate. b) A certain sample of calcium carbonate contains 4.86 mol. What is the mass in grams of this sample?
A.) 2.112 B.) 42,600 C.) 2.520 D.) none of these
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 O 2 gas. What volume is needed to hold that gas?
Juglone, a dye known for centuries, is produced from the husks of black walnuts. The formula for juglone is C 10 H 6 O 3. 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?
On a clean sheet of paper, show your work for 10-2 Practice Problems (1-3, 12-14, 17, 18, 23- 25).
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?
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.
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
Carvone is a substance that occurs in two forms, both of which have the same molecular formula (C 10 H 14 O) 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.
Individually, calculate the mass percents of the first three compounds on the worksheet. Let’s check your work.
Mass % is easily related to chemical formulas The relationship of moles to chemical formulas requires a little more thought...
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.
CH 2 O Calculate the mass percent of each element. C = 40% H = 6.7% O = 53.3% Isn’t this the reduced formula for: C 3 H 6 O 3, C 4 H 8 O 4, C 5 H 10 O 5, & C 6 H 12 O 6 Row 1: Calculate the mass percent of C 3 H 6 O 3. Row 2: Calculate the mass percent of C 4 H 8 O 4. Row 3: Calculate the mass percent of C 5 H 10 O 5. Row 4: Calculate the mass percent of C 6 H 12 O 6. The percentages (ratio) of the elements is the same with all of these formulas because they share the same reduced form.
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(CH 2 O) = glucose C 6 H 12 O 6
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.
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
Use a simple rhyme! % to gram Gram to mole Divide by the smallest Multiply ‘til whole.
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.
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.
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.
Molecular Formula= n(empirical formula) (Remember 6(CH 2 O) = 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
A white powder is analyzed and found to have an empirical formula of P 2 O 5. The compound has a molar mass of 283.88 g/mol. What is the compound’s molecular formula?
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.
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 O 2 gas in 2.5 L of O 2. 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.
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.
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.
1) Subtract. 2) % water lost =[water lost/hydrate mass]100 3) % water in hydrate = [5(water molar mass)/total molar mass] 100 4) Subtract. %water in hydrate - %water lost from your hydrate 5) % error = [#4 answer/#3 answer]100