THE MOLE General Chemistry Chemical Measurements Everyday people

THE MOLE General Chemistry

Chemical Measurements Everyday people perform jobs that require the ability to count and measure Chef- essential to measure ingredients correctly Construction worker- measuring cement, sand, gravel, and water determines the consistency of concrete Painter- adding the right mixture of colors creates new colors.

Chemical Measurements Dozen = 12 Can you Baker’s dozen = 13 imagine a mole of Gross= 144 donuts? 23 Mole (mol) = 6. 02 x 10 A mole of water molecules has a volume of only 18 m. L! Molecules are unbelievably small, so a lot of them doesn’t take up that much space. The mole is useful in chemistry because it links the microscopic world of atoms, molecules, and ions, to the macroscopic world

Avogadro’s Number 6. 02 x 1023 is so important in chemistry it’s given its own name… You guessed it, Avogadro’s Number In numerical form it looks like this: 602, 000, 000, 000 A mole of paper would reach passed Pluto A mole of basketballs is the size of Earth A mole of rice would cover the land masses of Earth to a depth of 75 meters!

Scientific Notation Practice Using the mole requires that we are comfortable using scientific notation Write the following in scientific notation 6000 0. 0067 78, 000 698, 700 0. 000009 0. 0090076 6. 00 x 103 6. 70 x 10 -3 7. 80 x 107 9. 00 x 10 -6 9. 01 x 10 -3 6. 99 x 105 Write the following in standard notation 6. 02 x 104 9. 03 x 109 7. 77 x 10 -2 9. 21 x 10 -7 60, 200 9, 030, 000 0. 0777 0. 000000921

The mole establishes a relationship between the atomic mass and the gram The mass in grams of 1 mole of a substance is equal to its atomic mass 6. 02 x 1023 atoms Cu = 63. 5 g = 1 mol Cu 6. 02 x 1023 atoms H = 1. 001 g = 1 mol H 6. 02 x 1023 atoms Fe = 55. 8 g = 1 mol Fe

What’s in a Mole? A mole of particles in an element is usually talking about atoms. The number of molecules in a mole of any molecular compound is 6. 02 x 1023

Molar Mass The mass in grams of 1 mole of a substance is called the molar mass of the substance. The molar mass of an element is equal to its atomic mass. The unit for molar mass is grams per mole, or g/mol

Molar Mass Ne = 20. 18 g/mol O 2 = 16. 00*2 = 32. 00 g/mol U = 238. 03 g/mol Na. OH = 22. 99 + 16. 00 + 1. 008 = 40. 00 g/mol CO 2 = 12. 01 + 16. 00*2 = 44. 01 g/mol Al 2(CO 3)3 = 26. 98*2 + (12. 01*3) + (16. 00*9) = 233. 99 g/mol

Moles to Grams Conversions If you know the mass of a substance, you can calculate the number of moles. You have 11. 2 g of Na. Cl. How many moles is that? 1. determine the molar mass of Na. Cl (using the periodic table) Na= 23. 0 g/mol Cl= 35. 5 g/mol 23. 0 g/mol + 35. 5 g/mol = 58. 5 g/mol (get these #’s from the periodic table)

Unit Analysis Method 1. 2. 3. Write down units asked for in answer to the right Write down the given value over 1 on the left Apply one or more unit factors to cancel units It’s as easy as 1 -2 -3!

Moles to Grams Conversions 1. 2. Molar mass of Na. Cl = 58. 5 g/mol Set up a conversion factor (a fraction whose value is equal to 1) 1. The units we need should be in the numerator and the units you already know in the denominator.

Moles to Grams Conversions You can also determine the mass of a sample if you know the number of moles 2. 50 mol of Na. Cl is how many grams? Set up a conversion factor

Moles to Grams Conversions MASS ar ol M g x mol = moles g s as g = g mol M moles x MOLES How many moles are in 14 g Li. OH? 14 g Li. OH 1 1 mol Li. OH 23. 95 g Li. OH 0. 58 mol Li. OH How many moles are in 15 g N 2? 15 g N 2 1 1 mol N 2 28. 02 g N 2 0. 54 mol N 2

Moles to Grams Conversions How many grams are in 4 mol H 2 O 2? 4 mol H 2 O 2 1 34. 016 g H 2 O 2 1 mol H 2 O 2 136. 06 g H 2 O 2 How many grams are in 56 mol Ca. CO 3? 56 mol Ca. CO 3 1 100. 09 g Ca. CO 3 1 mol Ca. CO 3 5605. 04 g Ca. CO 3

Moles to Molecules OR atoms The number of particles in 1 mole of any substance is always the same- Avogadro’s number. 6. 02 x 1023 particles 1 mol 6. 02 x 1023 particles or How many atoms are in 3 mol of elemental Ne? 23 3 mol Ne 1 6. 02 x 10 atoms 1 mol 1. 81 x 1024 atoms Ne

Moles to Molecules (cont. ) Molecules? ’s Nu m Use the subscript Av og ad ro 6. 02 x 1023 particles 1 mol Atoms be r PARTICLES 1 mol 6. 02 x 1023 particles MOLES How many atoms of oxygen are in 6 mol of O 2 molecules? 6 mol O 2 6. 02 x 1023 molecules O 2 2 atoms O 7. 22 x 1024 atoms O 1 1 mol O 2 1 molec. O 2 How many moles of I 2 are in 8. 02 x 1020 molecules of I 2? 8. 02 x 1020 molec. I 2 1 1 mol I 2 6. 02 x 1023 molecules I 2 1. 33 x 10 -3 mol I 2

Multistep Conversions MASS Use molar mass PARTICLES Avogadro’s Number MOLES You want to impress your date by boasting you know how many molecules of table sugar are in the cake you just made. You need 250 g of sugar (C 12 H 22 O 11). How many sucrose molecules will be in the cake? Plan: Convert the mass to moles using the molar mass and then convert to moles using Avogadro’s number. 250 g C 12 H 22 O 11 1 1 mol C 12 H 22 O 11 342. 3 g C 12 H 22 O 11 6. 02 x 1023 molecules 1 mol C 12 H 22 O 11 4. 4 x 1023 molec. C 12 H 22 O 11

Multistep Conversions If you burned 4. 0 x 1024 molecules of methane (CH 4) during a laboratory experiment, what mass of methane did you use? Plan: Convert your given # of molecules to moles using Avogadro’s number, then convert the moles to grams using the molar mass of methane. (12. 00 + 1. 004*4) 4. 0 x 1024 molec. CH 4 1 1 mol CH 4 6. 02 x 1023 molec. CH 4 16. 016 g CH 4 1 mol CH 4 106. 42 g CH 4