chapter4

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Slide1:

CHEMISTRY 161 Chapter 4 The Mole

Slide2:

Macroscopic versus Microscopic Worlds 2 H2 + O2 2 H2O 1 liter water contains about 3.3 X 1025 molecules

Slide3:

CHEMICAL MASS SCALE standard / calibration atomic mass unit (amu, u) one atom of carbon-12 12 u (exactly) we have to correlate u with kg

Slide4:

H2O O: 15.999 u H: 1.008 u H: 1.008 u H2O: 18.015 u PSE formula mass: weight of one molecule

Slide5:

CaO O: 15.999 u Ca: 40.08 u CaO: 56.08 u formula mass: weight of one molecule correlation between u and kg

Slide6:

MOLE

Slide7:

one mole of a compound contains the same number of molecules/atoms as the number of atoms in exactly 12 g of 12C Avogadro’s number Na 6.023 x 1023

Slide8:

1 mole of H2O 6.023 x 1023 1 mole of 12C 6.023 x 1023 6.023 x 1023 1 mole of NaCl 1 mole of Na 6.023 x 1023 Avogadro’s number links micro and macroscopic world molecules molecules atoms atoms

Slide9:

1 mole of H2O 6.023 x 1023 molecules 1 molecule of H2O – 2 H atoms and 1 O atom 1 mole of H2O – 2 mole H atoms and 1 mole O atoms 6.023 x 1023 molecules of H2O 6.023 x 1023 atoms of O 2 x 6.023 x 1023 atoms of H

Slide10:

H2O O: 15.999 u H: 1.008 u H: 1.008 u H2O: 18.015 u 1 mole of H2O – 18.015 g 15.999 g/mol 1.008 g/mol 1.008 g/mol Na Na Na

Slide11:

CaO O: 15.999 u Ca: 40.08 u CaO: 56.08 u 1 mole of CaO – 56.08 g

Slide12:

1 mole of H2O – 18.015 g 6.023 x 1023 molecules of H2O – 18.015 g one molecule of H2O – 2.99 x 10-23 g molecular weight of one mole of H2O 18.015 g mol-1

Slide13:

2 H2 + O2 2 H2O 2 molecules 1 molecule 2 molecules 2 moles 1 mole 2 moles 4.03176g 31.9988g 36.03g STOICHIOMETRY x g y g 70.0g

Slide14:

2 H2 + O2 2 H2O 2 molecules 1 molecule 2 molecules 2 moles 1 mole 2 moles 4.03176g 31.9988g 36.03g STOICHIOMETRY x g y g 70.0g

Slide15:

Example I: How many grams of iron are in a 15.0 g sample of iron(III) oxide? 1. molecular formula 3. weight of one mole Fe2O3 2. weight of one molecule Fe2O3 159.7 u 159.7 g 4. 1 molecule Fe2O3 contains 2 atoms of Fe 5. 1 mole Fe2O3 contains 2 moles of Fe 159.7 g 111.69 g 15.0 g x g x = 10.5 g

Slide16:

Example II: How many grams of oxygen are in a 10.0 g sample of nickel (II) nitrate? 1. molecular formula 3. weight of one mole Ni(NO3)2 2. weight of one molecule 4. 1 molecule Ni(NO3)2 contains 6 atoms of O 5. 1 mole Ni(NO3)2 contains 6 moles of O x = 5.25 g

Slide17:

Example III: How many atoms are in 10 kg of sodium? 1 mole sodium = 22.98977 g 6.023 x 1023 atoms = 22.98977 g x atoms = 10,000 g x = 2.6 x 1026 atoms

Slide18:

Example IV How heavy are 1 million gold atoms? 1 mole gold = 196.96654 g 6.023 x 1023 atoms = 196.96654 g 1,000,000 atoms = x g x = 3.2 x 10-16 g = 0.32 fg

Slide19:

Mass Percentage Composition P4O10 = X 100 % = X 100 %

Slide20:

Example V A sample was analyzed and contains 0.1417 g of nitrogen and 0.4045 g of oxygen. Calculate the percentage composition. 1. mass of whole sample 2. percentages of elements = X 100 %

Slide21:

EMPIRICAL FORMULA H2O H2O2 MOLECULAR FORMULA HO H2O H2O P4O10 P2O5 P2*2O2*5

Slide22:

Example A sample contains 0.522 g of nitrogen and 1.490 g of oxygen. Calculate its empirical formula. N2O5

Slide23:

COMBUSTION CxHy CO2 H2O

Slide24:

COMBUSTION C3H8 CO2 + H2O 0.013068 g + O2 How many grams of oxygen are consumed? balance equation convert to moles

Slide25:

The combustion of a 5.217 g sample of a compound of C, H, and O gave 7.406 g CO2 and 4.512 g of H2O. Calculate the empirical formula of the compound. How many grams of Al2O3 are produced when 41.5 g Al react? 2Al(s) + Fe2O3(s) Al2O3(s) + 2 Fe(s)