Problem Solving

Dimensional Analysis Used in conversion problems A method of keeping track of the units

Conversion Factor Conversion Factor – ratio of units that are related to one another Examples: 1 min = ____ sec  1 min / ___ sec or ———— Or vice versa: 60 sec = 1 min 7 days = 1 week  7 days/ 1 week 1000 m = 1 km  1 km/1000m 1 min 60 60 ___ sec 60

Use Dimensional Analysis Identify the GIVEN This is what the problem gives you Identify the UNKNOWN This is what you are trying to figure out Write your given Identify the correct CONVERSION FACTOR Think about what units to cancel Use conversion factors until you get to your unknown’s units Multiply all the top numbers and divide by all the bottom numbers

Convert 2.3 feet to inches One Step Conversions Some conversion factors: 2.54cm = 1 inch 12 inches = 1 foot 60 minutes = 1 hour 3 feet = 1 yard 24 hours = 1 day 1 mile = 5280 feet 60 seconds = 1 minute 365 days = 1 year

Convert 250 seconds to hours. Multiple Step Conversions Convert 250 seconds to hours. Some conversion factors: 2.54cm = 1 inch 12 inches = 1 foot 60 minutes = 1 hour 3 feet = 1 yard 24 hours = 1 day 1 mile = 5280 feet 60 seconds = 1 minute 365 days = 1 year

4. How many seconds are there in 5.74 hours? You Try! Get used to: Using conversion factors and setting it up the dimensional analysis way!! 1. How many days are there in 1.75 years? 2. How many feet are in 16 inches? 3. How many inches are in 5 miles? 4. How many seconds are there in 5.74 hours?

EXIT SLIP (show work!!!!) CHOOSE either a & c or b & c! Convert 2.5 miles to inches. Convert 555 seconds to hours Find the molar mass of the compound MgF2

EXIT SLIP (show work!!!!) CHOOSE one to do: Convert 2.5 miles to inches. Convert 555 seconds to hours Find the molar mass of the compound MgF2

Converting Units Answer Check! 7568.88 feet 28 carats 700 pounds 1.057 pints 0.047 tons 1040 ounces 1 cubic meter 109.8 km 0.035 miles 168,960 feet 157,680,000 seconds 316.8 inches 2.391 moles Na 79.2 inches 24.15 g Li 30.48 cm

The Mole So it’s Vday, and you wanted to buy a boquet of roses, and you wanted 12 or 24 roses, so you walk up to the florist, how would you ask it? Would you ask for 12 roses? Would you say the number. Or, example, you are in Dunkin Donuts, And you wanted 12 donuts, you would ask? You would ask for a dozen right? So a dozen represents a specific number of items.

What is a mole? Definition: the SI base unit to measure the amount of a substance. A mole is the number of carbon atoms in exactly 12 g of pure carbon Which means for 1 mol of C there are 12 grams! Mole describes the number of objects present The same thing, with the mole, it just represents a number. A mole is the number of carbon atoms in exactly 12g of pure carbon. So that means for 1 mol of carbon there are 12 grams That statement, might not make much sense right now, but what you should know, 1 mol equals 6.02E23. 6.02e23 representatives particle, a particle could be an atom, a molecule, a formula unit, an electron or an ion. This is called Avogadro’s number. So this number is HUGE. So what the 10 to the 23rd means, we’ll take a look at 4 x 10^3 which equals 4.  4000. so imagine it with the 23rd. So this number would not be good to talk about like referring to a bag of marbles. BUT it is good for talking aobout the quantities of like the atoms of copper, water and so forth. So we’re going to learn how to work with moles.

What is a mole? Mole = 6.02 x 1023 representative particles Avogadro’s Number The same thing, with the mole, it just represents a number. A mole is the number of carbon atoms in exactly 12g of pure carbon. So that means for 1 mol of carbon there are 12 grams That statement, might not make much sense right now, but what you should know, 1 mol equals 6.02E23. 6.02e23 representatives particle, a particle could be an atom, a molecule, a formula unit, an electron or an ion. This is called Avogadro’s number. So this number is HUGE. So what the 10 to the 23rd means, we’ll take a look at 4 x 10^3 which equals 4.  4000. so imagine it with the 23rd. So this number would not be good to talk about like referring to a bag of marbles. BUT it is good for talking aobout the quantities of like the atoms of copper, water and so forth. So we’re going to learn how to work with moles.

What is a mole? Mole = 6.02 x 1023 representative particles 602,200,000,000,000,000,000,000 The same thing, with the mole, it just represents a number. A mole is the number of carbon atoms in exactly 12g of pure carbon. So that means for 1 mol of carbon there are 12 grams That statement, might not make much sense right now, but what you should know, 1 mol equals 6.02E23. 6.02e23 representatives particle, a particle could be an atom, a molecule, a formula unit, an electron or an ion. This is called Avogadro’s number. So this number is HUGE. So what the 10 to the 23rd means, we’ll take a look at 4 x 10^3 which equals 4.  4000. so imagine it with the 23rd. So this number would not be good to talk about like referring to a bag of marbles. BUT it is good for talking aobout the quantities of like the atoms of copper, water and so forth. So we’re going to learn how to work with moles.

One mole of anything has What is a mole? One mole of anything has 602,200,000,000,000,000,000,000 items or 6.02 x 1023 items The same thing, with the mole, it just represents a number. A mole is the number of carbon atoms in exactly 12g of pure carbon. So that means for 1 mol of carbon there are 12 grams That statement, might not make much sense right now, but what you should know, 1 mol equals 6.02E23. 6.02e23 representatives particle, a particle could be an atom, a molecule, a formula unit, an electron or an ion. This is called Avogadro’s number. So this number is HUGE. So what the 10 to the 23rd means, we’ll take a look at 4 x 10^3 which equals 4.  4000. so imagine it with the 23rd. So this number would not be good to talk about like referring to a bag of marbles. BUT it is good for talking aobout the quantities of like the atoms of copper, water and so forth. So we’re going to learn how to work with moles.

Mass to Moles Problem: Find how many moles are in 525 grams of calcium What is the molar mass of Calcium? (Periodic Table) Given: Unknown: number of grams = 525g Ca molar mass Ca = 40.08 g/mol Ca moles of Ca = ? mol Alright, so we can go from mass to moles as well. So if we are given the problem. Now we have a conversion factors, grams per mol. What are we given? What did they give us in the problem? what’s our molar mass? What’s our unknown, what are we looking for? Let’s make our chart. 525 g Ca 1 mol Ca 13.1 mol Ca 40.08 g Ca

Moles to Mass Problem: Find the number of grams in .045 moles of Barium Chloride. What is the molar mass of Barium Chloride? (Periodic Table) Given: Unknown: number of moles = .0450 mol BaCl2 molar mass BaCl2 = 208.33 g/mol BaCl2 mass of BaCl2 = ? g BaCl2 Now we have a conversion factors, grams per mol. What are we given? What did they give us in the problem? what’s our molar mass? What’s our unknown, what are we looking for? Let’s make our chart. .0450 mol BaCl2 208.33 g BaCl2 9.37 g BaCl2 1 mol BaCl2

Practice Problems: Moles-Mass Determine the number of grams in 2.5 moles of Sodium Fluoride. Determine the number of moles in 15.5 grams of Potassium.

Converting Units WS 1 Per 1 28 carats 1.057 pint 1040 ounces 109.83 km 168,960 ft 79.2 in 58.5 g/mol, 98 g/mol, 115.7 g/mol 0.427 mol NaCl 0.867 mol H2SO4 406 g Li3PO4 49 g Challenge: 33.6 L

Molar Mass Conversions Mixed Problems! 0.43 mol 64 g O2 1.274 mol 3.07 mol H2O 0.632 mol 121.5 g HBr 0.992 mol 0.172 mol Ca3N2 0.219 mol 2.023 mol C3H6 33.6 L CO2 146.25 g 49.05 g 268.77 g 18.65 g 511.008 g

TAKE OUT MOLE NOTE PACKET Units of volume are Liters

22.4 L 1 mol and 1 mol 22.4 L Molar Volume Molar volume of a gas is the volume that 1 mol occupies at 0°C and 1 atm of pressure. The 0°C and 1 atm are known as the Standard Temperature and Pressure (STP) 1 mol of any gas occupies a volume of 22.4 L at STP Conversion Factor: 1 mol of any gas occupies a volume of 22.4L 22.4 L 1 mol and 1 mol 22.4 L Units of volume are Liters

Moles to Volume Problem: What is the volume of 2 moles of Oxygen? Given: Unknown: What’s our conversion factor? 2 mol O2 volume of O2 = ? L O2 22.4 L mol Now we have a conversion factors, grams per mol. What are we given? What did they give us in the problem? what’s our molar mass? What’s our unknown, what are we looking for? Let’s make our chart. 2.0 mol O2 22.4 L O2 44.8 L O2 1 mol O2

Practice Problems Determine the number of liters in 3.5 moles of Nitrogen gas Determine the number of liters in 1.5 moles of Oxygen gas.

Grams to Volume Problem: Find how many liters are in 10 grams of Hydrogen gas  Different type of problem. Given: Unknown: What’s our conversion factor(s)? 10 g H2 number of liters H2 = ? L H2 2 22.4 L mol 2.02 g H2 mol H2 Now we have a conversion factors, grams per mol. What are we given? What did they give us in the problem? what’s our molar mass? What’s our unknown, what are we looking for? Let’s make our chart. 10 g H2 1 mol H2 22.4 L H2 112 L H2 1 mol H2 2 g H2

What is the number associated with the mole? Mole = 6.02 x 1023 representative particles Representative Particles can be: Most Elements Atom Diatomic Elements Molecule Molecular Compounds Ionic Compounds Formula Unit *When you see these words use 6.02 x 1023 The same thing, with the mole, it just represents a number. A mole is the number of carbon atoms in exactly 12g of pure carbon. So that means for 1 mol of carbon there are 12 grams That statement, might not make much sense right now, but what you should know, 1 mol equals 6.02E23. 6.02e23 representatives particle, a particle could be an atom, a molecule, a formula unit, an electron or an ion. This is called Avogadro’s number. So this number is HUGE. So what the 10 to the 23rd means, we’ll take a look at 4 x 10^3 which equals 4.  4000. so imagine it with the 23rd. So this number would not be good to talk about like referring to a bag of marbles. BUT it is good for talking aobout the quantities of like the atoms of copper, water and so forth. So we’re going to learn how to work with moles.

Moles to Particles Problem: How many particles of oxygen are in 0.75 moles of oxygen?

Particles to Grams Problem: Determine the number of grams in 12.04 x 1023 molecules of carbon monoxide.

Particle Practice Problems Determine the number of grams in 3.01 x 1023 molecules of BF3 Determine the number of particles in 32 grams of NaCl

Overview Molar Mass = grams  tells us how much mass it has (heavy) Use MOLAR MASS to convert Molar Volume = liters  tells us how much space it takes up (must be at STP to use) Use 22.4 L/mol to convert Particles/Atoms = tells us how many atoms/particles there are Use 6.02 x 1023 to convert

Acc Converting Worksheets  Check your Work Acc Molar Volume Practice 33.6 mol O2 1 mol N2 0.27 mol CO2 21 L O2 22.91 L CO2 18.75 g N2 257.5 g NaBr Converting Units 28 carats 1.057 pints 1040 ounces 109.8 km 168,960 feet 316.8 inches 79.2 inches 30.48 cm 7568.88 feet 700 pounds 0.047 tons 1 cubic meter 0.035 miles 157,680,000 seconds 2.391 moles Molar Mass Conversions 0.43 mol 1.274 mol 0.632 mol 0.992 mol 0.219 mol 146.25 g 49.05 g 268.77 g 18.65 g 511.008 g Mixed Probs on FRONT: 64 g O2 3.07 mol H2O 121.5 g HBr