The factor label method

Slides:



Advertisements
Similar presentations
The factor label method
Advertisements

Chapter 12 Stoichiometry
Measurement in Chemistry Factor-Label Method
Dimensional Analysis (aka Factor-Label)
Chemical Quantities.  Calculate the mass of compounds.  Calculate the volume of a given mass of a gas from its density at a given temperature and pressure.
REALLY, REALLY SMALL NUMBERS.
Chapter 12 Stoichiometry Mr. Mole. Molar Mass of Compounds Molar mass (MM) of a compound - determined by up the atomic masses of – Ex. Molar mass of CaCl.
Before the Bell Rings Collect all handouts. DO NOT TRY TO SOLVE ANY PROBLEMS!!!! Have out bellwork sheet. Be ready to begin when the bell rings. Honors:
The factor label method u A way to solve math problems in chemistry u Used to convert km to miles, m to km, mol to g, g to mol, etc. u To use this we.
Unit Conversions Q - How many kilometers are in 47 miles? (note: 1 km = miles) First identify the desired quantity. # km.
A way to solve math problems in science Used to convert km to miles, m to km, mol to g, g to mol, etc. To use this we need: 1) desired quantity, 2) given.
Unit Ten: Introducing the Mole
A way to solve math problems in chemistry Used to convert km to miles, m to km, mol to g, g to mol, etc. To use this we need: 1) desired quantity, 2)
Practice with Molar Mass Problems. :Question #1 How many moles of H 2 are in 100 g of H 2 ? # mol H 2 = 100 g H 2 x 1 mol H g H 2 = 49.5 mol H.
Measurement in Chemistry Factor-Label Method The Factor-Label Method At the conclusion of our time together, you should be able to: 1.Recognize a problem.
Chemical Quantities.  Calculate the mass of compounds.  Calculate the volume of a given mass of a gas from its density at a given temperature and pressure.
Measurement in Chemistry Factor-Label Method
Conversion Factors and Unit Cancellation A physical quantity must include: Number + Unit + Unit.
Practice with Molar Mass Problems. :Question #1 How many moles of H 2 are in 100 g of H 2 ? # mol H 2 = 100 g H 2 x 1 mol H g H 2 = 49.5 mol H.
Moles Unit Dimensional Analysis.
Measurement in Chemistry Factor-Label Method The Factor-Label Method At the conclusion of our time together, you should be able to: 1.Recognize a problem.
A way to solve math problems in chemistry Used to convert km to miles, m to km, mol to g, g to mol, etc. To use this we need: 1) desired quantity, 2)
Using a balanced equation to convert units of a chemical.
Aim: How to calculate Percent Composition  DO NOW: 1. What is the number of moles of potassium chloride present in 148 g? 2. What is the molar mass of.
Stoichiometry: Formulas and the Mole Lincoln High School 1.
Compound Stoichiometry. The Mole Unit for dealing with the number of atoms, ions, or molecules in a common sized sample Relationship between Moles and.
A way to solve math problems in chemistry Used to convert km to miles, m to km, mol to g, g to mol, etc. To use this we need: 1) desired quantity, 2)
Quantitative Chemistry Chemistry 10 Handy Math Skills.
Stoichiometry Chapter 12. Chocolate Chip Cookies!! 1 cup butter ;1/2 cup white sugar 1 cup packed brown sugar 1 teaspoon vanilla extract 2 eggs ; 2 1/2.
Stoichiometry. Review: Dimensional Analysis Goal: To make the units cancel out Strategy: Start out with the quantity given that you are trying to convert.
Stoichiometry.
Stoichiometry II.
Stoichiometry.
Stoichiometry Review.
6.3/6.4 The Mole and Molar Mass
Stoichiometry (Ch 12) Stoichiometry is the calculation of amounts of substances involved in a chemical reaction. Coefficients in chemical reactions show.
Stoichiometry 1 Formulas and the Mole
Warm-up How many grams are in 3.45 X 104 formula units of iron (II) oxide?
Stoichiometry Chemistry I: Chapter 11
Conversion factors Conversion factors for 1 ft = 12 in
Unit 19 Calculations with the Mole
First write down the desired quantity
Moles.
Bellringer How many pounds do you weigh? How many ounces?
Stoichiometry.
Practice: 2 step mole conversions
Stoichiometric Calculations
STOICHIOMETRY BASICS Chemistry.
Chapter 9 Balancing Equations Limiting Reagents
Stoichiometry (Ch 12) Stoichiometry is the calculation of amounts of substances involved in a chemical reaction. Coefficients in chemical reactions show.
The factor label method
N2K (08/30/17) The mass of a lump of gummy bears is 313.6g. If each gummy bear weighs 3.2g, how many gummy bears are in the lump? The mass of a copper.
Stoichiometry Chemistry I: Chapter 11
Stoichiometry.
The Mole and Stoichiometry
Stoichiometry.
Scientific Notation and Factor Label Method
N2K (08/30/17) The mass of a lump of gummy bears is 313.6g. If each gummy bear weighs 3.2g, how many gummy bears are in the lump? The mass of a copper.
Bellringer I have 2 eggs. How many cookies can I make?
Dimensional Analysis I
Problem Solving.
The Mole and Stoichiometry
The factor label method
Chapter 12 Stoichiometry
Dimensional Analysis (aka Factor-Label)
Quantities in Chemistry
QOTD What is atomic mass? How is atomic mass determined?
Stoichiometry.
Stoichiometry.
Stoichiometry Chemistry I: Chapter 12 Chemistry I HD: Chapter 9
Presentation transcript:

The factor label method A way to solve math problems in chemistry Used to convert km to miles, m to km, mol to g, g to mol, etc. To use this we need: 1) desired quantity, 2) given quantity, 3) conversion factors Conversion factors are valid relationships or equities expressed as a fraction E.g. for 1 km=0.6 miles the conversion factor is Q. write conversion factors for 1 foot =12 inches Q. what conversion factors can you think of that involve meters?

Conversion factors Conversion factors for 1 ft = 12 in There are almost an infinite number of conversion factors that include meters:

Conversion factors We have looked at conversion factors that are always true. There are conversion factors that are only true for specific questions E.g. A recipe calls for 2 eggs, 1 cup of flour and 0.5 cups of sugar We can use these conversion factors Q - the chemical equation between H2 and O2 involves 2 H2 molecules combining with 1 O2 molecule to make 2 H2O molecules. Write all possible conversion factors

2H2 + O2  2H2O 2 molecules H2 1 molecule O2 2 molecules H2 2 molecules H2O 1 molecule O2 2 molecules H2O 2 mol H2 1 mol O2 2H2 + O2  2H2O 2 mol H2 2 mol H2O 1 mol O2 2 mol H2O

The steps to follow Now we are ready to solve problems using the factor label method. The steps involved are: Write down the desired quantity/units Equate the desired quantity to given quantity Determine what conversion factors you can use (both universal and question specific) Multiply given quantity by the appropriate conversion factors to eliminate units you don’t want and leave units you do want Complete the math

First write down the desired quantity Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) # km First write down the desired quantity

Next, equate desired quantity to the given quantity Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) # km = 47 mi Next, equate desired quantity to the given quantity

Now we have to choose a conversion factor Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) # km = 47 mi Now we have to choose a conversion factor

What conversion factors are possible? Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) # km = 47 mi 1 km 0.621 mi 0.621 mi 1 km What conversion factors are possible?

Pick the one that will allow you to cancel out miles Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) # km = 47 mi 1 km 0.621 mi 0.621 mi 1 km Pick the one that will allow you to cancel out miles

Pick the one that will allow you to cancel out miles Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) # km = 47 mi 1 km 0.621 mi 0.621 mi 1 km Pick the one that will allow you to cancel out miles

Multiply given quantity by chosen conversion factor Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) # km = 47 mi 1 km 0.621 mi 0.621 mi 1 km Multiply given quantity by chosen conversion factor

Multiply given quantity by chosen conversion factor Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) x 1 km 0.621 mi # km = 47 mi Multiply given quantity by chosen conversion factor

Cross out common factors Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) x 1 km 0.621 mi # km = 47 mi Cross out common factors

Cross out common factors Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) x 1 km 0.621 # km = 47 Cross out common factors

Are the units now correct? Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) x 1 km 0.621 # km = 47 Are the units now correct?

Yes. Both sides have km as units. Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) x 1 km 0.621 # km = 47 Yes. Both sides have km as units.

Yes. Both sides have km as units. Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) x 1 km 0.621 # km = 47 Yes. Both sides have km as units.

Factor label example Now finish the math. Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) x 1 km 0.621 = 75.7 km # km = 47 Now finish the math.

Factor label example The final answer is 76 km Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) x 1 km 0.621 = 75.7 km = 76 km # km = 47 The final answer is 76 km

Summary The previous problem was not that hard In other words, you probably could have done it faster using a different method However, for harder problems the factor label method is easiest

More examples You want to buy 100 U.S. dollars. If the exchange rate is 1 Can$ = 0.65 US$, how much will it cost? # Can$ = 100 US$ x 1 Can$ 0.65 US$ = 153.85 Can$ = 150 Can $ One mole of a gas has a volume of 22.4 L. How many L will 300. grams of CO2 occupy? (hint: the molar mass of CO2 is ____ g/mol). 44.01 # L CO2 = 300. g CO2 x 1 mol CO2 44.01 g CO2 x 22.4 L CO2 1 mol CO2 = 152.7 L = 153 L

More examples There are 12 inches in a foot, 0.394 inches in a centimeter, and 3 feet in a yard. How many cm are in one yard (1.00 yards) ? # cm =1.00 yd x 3 ft 1 yd x 12 in 1 ft x 1 cm 0.394 in = 91.37 cm = 91.4 cm A chemical reaction requires 3.000 moles of sodium chloride. How many grams is this? Sodium chloride is NaCl (58.44 g/mol) #g NaCl = 3.000 mol NaCl x 58.44 g NaCl 1 mol NaCl = 175.3 g NaCl

Assignment Answer questions using the factor label method: How many moles of H2 are in 100. g of H2? 300. g of CuSO4 is needed in an experiment. How many moles does this represent? A chemical reaction requires 23.78 moles of silver chloride. How many grams is this? Calculate how many feet are in 1.00 meter (use information from the examples above). With a U.S. dollar you can buy 1.1 Euros, 130 Yen, or 25 Rubles. How many Yen can you buy with one Ruble?

Assignment How many molecules are in 73 grams H2O? (hint: form a conversion factor using Avogadro’s #) 255 g of calcium phosphate are produced in a chemical reaction. How many moles of calcium phosphate does this represent? According to the equation 2H2 + O2  2H2O, how many grams of H2O would be produced if 7.35 mol of O2 is used up? (hint: you will need two conversion factors – 1 from the balanced equation and 1 from a molar mass)

1. # mol H2 = 100. g H2 x 1 mol H2 2.02 g H2 = 49.5 mol H2 2. # mol CuSO4 = 300. g CuSO4 x 1 mol CuSO4 159.61 g CuSO4 = 1.88 mol CuSO4 3. # g AgCl = 23.78 mol AgCl x 143.32 g AgCl 1 mol AgCl = 3408 g AgCl 4. # ft = 1.00 m x 100 cm 1 m x 0.394 in 1 cm x 1 ft 12 in = 3.28 ft

5. # Yen = 1 Ruble x 1 US $ 25 Rubles x 130 Yen 1 US $ = 5.2 Yen # H2O molecules = 6. 73 g H2O x 1 mol H2O 18.02 g H2O x 6.02x1023 molecules 1 mol H2O = 2.44 x 1024 molecules H2O 7. # mol Ca3(PO4)2 = 255 g Ca3(PO4)2 x 1 mol Ca3(PO4)2 310.18 g Ca3(PO4)2 = 0.822 mol Ca3(PO4)2 8. # g H2O= 2 mol H2O 1 mol O2 x 18.01 g H2O 1 mol H2O x 265 g H2O = 7.35 mol O2

Assignment Complete the following chart: Formula Molar mass (g/mol) Moles (mol) FeSO4 500. (NH4)2CO3 2.00 SnO2 50. Sb2O5 0.250 NaClO4 100. Mg(IO3)2 3.200 CoCl2.H2O 332

Assignment Complete the following chart: Formula Molar mass (g/mol) Moles (mol) FeSO4 151.9 500. 3.29 (NH4)2CO3 96.1 192.2 2.00 SnO2 150.7 50. 0.33 Sb2O5 323.6 80.9 0.250 NaClO4 122.4 100. 0.817 Mg(IO3)2 374.1 1196.8 3.200 CoCl2.H2O 147.8 332 2.25

Assignment 1. How many grams are there in 2.000 moles of silver chloride? 2. How many moles does 100. g of hydrogen gas represent? 3. How many moles are there in 300. g of copper (II) carbonate? 4. How many moles are in 250. g of potassium hypochlorite?

Assignment AgCl = 143.35 g/mol #g = 2.000 mol x 143.35 g/mol = 286.7 g H2 = 2.016 g/mol #mol = 100. g x mol/2.016 g = 49.6 mol CuSO4 = 159.62 g/mol #mol= 300. g x mol/159.62 g=1.879 mol KClO = 90.55 g/mol #mol = 250. g x mol/90.55 g = 2.76 mol