3Terms for specific counts…pair, dozen, etc. 1 dozen apples = 12 apples.1 dozen apples = 2.0 kg apples.1 dozen apples = 0.2 bushels apples.Ratios: 1 dozen apples/12 apples1 dozen apples/2.0 kg apples1 dozen apples/0.2 bushels apples
4Problem… What is the mass of 90 apples if 1 dozen apples = 2.0 kg? Analyze…known…# of apples = 9012 apples = 1 dozen1 dozen = 2.0 kgUnknown…mass of 90 apples = ?kg
6Evaluate Does it make sense? Practice…What is the mass of 0.5 bushels of apples?Practice…assume 8 seeds per apple. How many seeds are in 14 kg of apples?
7What is a Mole?A specified number of particles. Used by chemists x 1023 representative particles (Avagrado’s number).Representative particles can be atoms, molecules, or formula units.Ratio: 1 mole/6.02x1023 rep. particles
8Scientific basis of the mole 6.02x1023 is the number of atoms in 12 grams of Carbon-12.If one mole of carbon-12 atoms were weighed, it would weigh exactly 12 grams.
9Atoms to moles How many moles in 1.25x1023 atoms of magnesium? Known; # of atoms = 1.25x10231 mole = 6.02x1023 atoms Mg.Unknown; moles of magnesium.Calculate…
10Moles to # of particlesHow many atoms in a mole? First determine how many atoms in a representative particle.How many atoms in 2.12 moles of propane (C3H8)?Known: # of moles of C3H8 is mole = 6.02x1023 molecules C3H8. 1 molecule C3H8 = 11 atoms.Unknown: # of atoms.
11Calculate…Practice…How many atoms in 1.14 moles SO3?How many moles in 4.65x1024 molecules NO2?
12The Mass of a Mole of an Element Mass of atoms expressed in amu’s (atomic mass units), which are relative units based on the isotope Carbon-12 (12.0 amu).C-12 is twelve times heavier than an average hydrogen atom with a mass of 1.0 amu.100 C-12 atoms are 12 times heavier than 100 hydrogen atoms.
13Any number of C-12 atoms are always twelve times heavier than the same number of hydrogen atoms. The mass ratio of 12 carbon atoms to 1 hydrogen atom is the same regardless of the units used to express the mass.Therefore, 12.0 g of carbon atoms and g of hydrogen atoms must have the same number of atoms.
14Representative Particle Smallest unit in a substanceCan be different thingsOne atom (metals, atomic substances)One molecule (molecular compounds)One ion (charged atoms or molecules)One formula unit (ionic compounds)
16Measuring Chemical Substances Using Avogadro’s number: a specific number of representative particles6.02 x 1023 RP/moleReferred to as one mole (mol)Example: One mol water contains6.02 x 1023 H20 moleculesExample: one mole nitrogen gas…
17Practice Q: how many moles does 1.25 x 1023 atoms of Mg represent? A: 1.25 x 1023 Mg atoms x (6.03 x 1023 RP)/mole =0.2 molesQ: how many moles does 2.8 x 1024 atoms of silicon have?A: 2.8 x 1024 Si atoms/6.03 x 1023 RP/mole =4.6 molesQ:Q: How many propane (C3H8) molecules are in 2.12 mol of C3H8 ?A: 2.12 moles x (6.03 x 1023 ) RP/mole = 12.8
18Converting molecular Moles into Number of individual atoms Hint: when asked for # of atoms always doMoles #molecules #atoms
19Practice Q: How many atoms are in 2.12 mol of C3H8 ? First calculate how many moleculesA: 2.12 moles x (6.02 x 1023 RP)/mole= x 1023 RP = 1.28 x 1024 RPThen calculate how many atomsEach RP (C3H8) has 11 atoms/RPMultiply with 11: 1.28 x 1024 RP x 11 Atoms/Rp=14.08 X 1024 atomsClean all results to single digit number!!!14.08 X → Atoms = 1.4 x 1025 atoms
20Practice You have 4.65 x 1024 molecules of NO2? Q: How many atoms? A: RP NO2 has three atoms/molecule3 atoms/molecule x 4.65 x 1024 molecules
21The mass of one mole of a given element Mass of an element is indicated in the periodic table as the mass numberCalled amu = atomic mass unitamu is the mass (in grams) of one mole of this elementRemember it is an average number of the different isotopes…it has decimals
22Finding mass What is the mass of one mole O, P, K, S-33, 146C Atomic oxygen: g/moleAtomic phosphorus: g/moleAtomic potassium: g/moleAtomic S-33: g/moleAtomic 146C: g/mole
23How many mole in a given mass How many moles of Carbon are found in 52 g?52 g/12.01 g/mole C= 4.33 moles C
24Practice calculating molar masses Q: How many moles of C-14 are found in 34 g?34 g x mole C-14/14g C-14 = 2.42 moles C-14Q: What mass does 6.02 x 1023 atoms of Hydrogen have?Is one mole → 1.01 gQ: What is the mass of 2.34 x 1022 atoms of phosphorus? First find how many moles2.34 x 1022 atoms x mole/6.02 x 1023 atoms = 0.04 moles P0.04 moles P x g/mole = 1.24 g
25Mass of a Mole of a Compound Example: SO3What type of compound?How many atoms of S and O?Add up amus of S and O32.1 amu amu amu amu = 80.1 amuOne mole SO3 weighs 80.1 g
26Practice: find the molar masses Find the molar mass ofWaterGlucoseCarbon dioxide
27Practice Q:How many moles of glucose are in 200 g? Molar mass of glucose is g/moleA: 200g x mole/ g = 1.11 molesQ: How many molecules of glucose is this?6.02 x1023 RP/mole x 1.11 moles = 6.7 x molecules glucose