1. The Mole Concept

2. What is a mole? IIn chemistry, a mole is a counting unit. Abbreviated mol. 11 mol = 6.022x10 23 representative particles. Avogadro’s Number (N) WWhat is a representative particle? A unit that represents what the mole is counting.

3. About Scientific Notation in Calculators HHow do you represent 6.022x10 23 in a scientific calculator? DDo you punch in 6.022x10^23? You can, but there’s a better way. FFor graphing calculators: Type in 6.022(2 nd )(,)23 The calc. displays 6.022E23 This means “6.022x10 23 ” to the calculator. FFor other calculators there is usually a key marked “E” or “EXP” that allows you to enter numbers in scientific notation. Learn how to use your calculator!

4. Representative Particles SSubstance / Representative Particle Elements / Atoms Ions / Ions Covalent Compounds / Molecules Ionic Compounds / Formula Units

5. IIf you have 3 representative particles of water, what do you have? You have 3 water molecules. H 2 O is a molecular compound. IIf you have 4 representative particles of table salt, what do you have? You have 4 NaCl formula units. NaCl is an ionic compound. IIf you have 5 representative particles of gold, what do you have? You have 5 gold atoms. Gold is an element.

6. 3 water molecules 4 NaCl formula units 5 gold atoms

7. How Big is Avogadro’s Number? 66.022x10 23 dollars would be enough to give every person on Earth $87 trillion. That’s $1 million a second for the next 2.8 years. AA modern computer that can make up to 100 million counts per second would take almost 200 million years to count to 6.022x10 23. IIf 6.022x10 23 snowflakes fell evenly across the United States, the blanket of snow would cover every building in the country, including the tallest skyscrapers. IIf you could travel at the speed of light (186,000 mi/s in a vacuum), it would take you more than 100 billion years (longer than the Universe has been around) to travel 6.022x10 23 miles.

8. Mole-Particle Conversions HHow many molecules of methane are in 4.50 mol methane? 1 mol CH 4 = 6.022x10 23 CH 4 molecules 4.50 mol CH 4 x 6.022x10 23 molecules CH 4 1 mol CH 4 = 2.71x10 24 molecules CH 4

9. Mole-Particle Conversions HHow many moles of iron are in 2.39x10 24 iron atoms? 1 mol Fe = 6.022x10 23 Fe atoms 2.39x10 24 atoms Fe x 6.022x10 23 atoms Fe 1 mol Fe = 3.97 mol Fe

10. Molar Mass RRepresentative particles are too tiny to count directly. If we know how much these particles weigh, we can count them by weighing them. MMolar mass = mass of 1 mole of a substance. Unique for every substance.

11. Calculating Molar Mass MMolar mass of an element = atomic mass. Atomic mass of Fe = 55.847 amu Molar mass of Fe = 55.847 g/mol EEvery 55.847 grams of iron contains 6.022x10 23 iron atoms! We can weigh a sample of pure iron and then calculate how many atoms it contains!

12. Moles and Mass WWhat is the mass of 0.250 moles of magnesium? 1 mol Mg = 24.305 g Mg 0.250 mol Mg x 24.305 g Mg 1 mol Mg = 6.08 g Mg

13. Moles and Mass HHow many atoms of mercury are in 3.15x10 -5 g Hg? Always go to moles first! 1 mol Hg = 200.59 g Hg 1 mol Hg = 6.022x10 23 atoms Hg 3.15x10 -5 g Hg x 1 mol Hg 200.59 g Hg = 9.46x10 16 Hg atoms 6.022x10 23 Hg atoms 1 mol Hg x

14. Calculating Molar Mass MMolar mass of a compound = Combined molar mass of its elements, multiplied by subscripts. Molar mass of H 2 O = 22 x H = 2 x 1.01 g/mol = 2.02 g/mol 11 x O = 1 x 16.00 g/mol = 16.00 g/mol TTotal = 18.02 g/mol EEvery 18.02 grams of water contains 6.02x10 23 water molecules!

15. Molar mass of Fe(NO 3 ) 3 11 x Fe = 1 x 55.85 g/mol = 55.85 g/mol 33 x N = 3 x 14.01 g/mol = 42.03 g/mol 99 x O = 9 x 16.00 g/mol = 144.00 g/mol TTotal = 241.88 g/mol EEvery 241.88 grams of iron(III) nitrate contains 6.02x10 23 formula units of Fe(NO 3 ) 3 !

16. Mole-Mass Conversions WWhat is the mass of 0.245 mol CH 4 ? First, find molar mass of CH 4 : 11 x C = 1 x 12.01 g/mol = 12.01 g/mol 44 x H = 4 x 1.01 g/mol = 4.04 g/mol TTotal = 16.05 g/mol 0.245 mol CH 4 x 16.05 g CH 4 1 mol CH 4 = 3.93 g CH 4

17. Mole-Mass Conversions HHow many moles are in 26.64 grams of calcium acetate? First we need a formula: CCalcium acetate = Ca(C 2 H 3 O 2 ) 2 Next we need the molar mass: 11 x Ca = 1 x 40.08 g/mol = 40.08 g/mol 44 x C = 4 x 12.01 g/mol = 48.04 g/mol 66 x H = 6 x 1.01 g/mol = 6.06 g/mol 44 x O = 4 x 16.00 g/mol = 64.00 g/mol TTotal = 158.18 g/mol 26.64 g Ca(C 2 H 3 O 2 ) 2 x 158.18 g Ca(C 2 H 3 O 2 ) 2 1 mol Ca(C 2 H 3 O 2 ) 2 = 0.1684 mol Ca(C 2 H 3 O 2 ) 2

18. Mole-Mass-Particle Conversions molesgramsparticles Use molar mass Use 6.022x10 23

19. The Commandments of Moles TThou shalt not use 6.022x10 23 when converting from grams to moles or from moles to grams. Thou shalt instead use the molar mass. TThou shalt not use the molar mass when converting from particles to moles or from moles to particles. Thou shalt instead use 6.022x10 23. TThou shalt not attempt to convert from grams to particles in one step. Thou shalt instead go to moles first.