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 moleSolve dimensional analysis problems

HOMEWORK:See your calendar!

MEET THE MOLE.

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

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?

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.

AVOGADRO’S NUMBER 6.022x1023

My pet mole is named Avogadro.

DEFINING THE MOLE Counting Weighing Amount of Space Needed

Let’s represent our 3 mole definitions in a graphic organizer.

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 CH41 C = 12.011 g C4 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. RECORD YOUR ANSWER TO TWO DECIMAL PLACES.

EXAMPLE 6.5

EXAMPLE 6.5 Calculate the molar mass of sulfur

dioxide, a gas produced when sulfur-containing fuels are burned.

SO2S = 32.07 gO = 2(16.00 g)Total = 64.07 g/molCan also be expressed as 1 mol SO2 =

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 C2H3CL. CALCULATE THE MOLAR MASS OF THIS SUBSTANCE. RECORD THE ANSWER TO TWO DECIMAL PLACES.

PRACTICE PROBLEMS 6.5

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

LEARNING TO USE THE MOLE MAP Using the Mole Concept to Calculate

Page 182-7 EX 6.3, EX 6.4, EX. 6.6

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?

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

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

EXAMPLE 6.4 (INDEPENDENT)

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.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?

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

PRACTICE PROBLEM 6.6

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?

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?

PARTNER PRACTICE

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

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?

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.

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

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.

PERCENT BY MASS WORKSHEET Individually, calculate the mass percents

of the first three compounds on the worksheet.

Let’s check your work.

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...

TYPE OF CHEMICAL FORMULA: EMPIRICAL FORMULA Empirical formula: lowest whole

number ratio of the atoms of the elements in a compoundIonic 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.

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.

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) = glucoseC6H12O6

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.

WHAT IS SHE TALKING ABOUT? White powder found in the hallway Mass spectroscopy instrument used to

analyze the unknown powderData 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

CALCULATING EMPIRICAL FORMULA Use a simple rhyme!

% to gramGram to moleDivide by the smallestMultiply ‘til whole.

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 YOUGram to mole = dimensional analysisLet’s carry out the calculation on the

board.

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.

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.

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

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?

PRACTICE PROBLEM 6.15 A compound used as an additive for

gasoline to help percent engine knock shows the following percentage composition:71.65% Cl24.27% C4.07% HThe molar mass is known to be 98.96 g.

Determine the empirical formula and the molecular formula for this compound.

INDIVIDUAL PRACTICE Page 208 4-6

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.

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.

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.

CALCULATIONS HINTS1) Subtract.2) % water lost =[water lost/hydrate

mass]1003) % 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