Lec04 Mole Concept - THE MOLE CONCEPT A number of atoms...

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LALaput Chemistry 16 Lecture 4 THE MOLE CONCEPT •A number of atoms, ions, or molecules that is large enough to see and handle. •A mole = number of things –Just like a dozen = 12 things –One mole = 6.022 x 10 23 things •Avogadro’s number = 6.022 x 10 23 –Avogadro’s number = N A The mass of one mole of atoms of a pure element in grams ( molar mass ) is equal to the atomic weight of the element in atomic mass units. CHEMICAL FORMULAS •Chemical formula shows the chemical composition of the substance. ratio of the elements present in the molecule or compound •He, Au, Na –monatomic elements •O 2 , H 2 , Cl 2 –diatomic elements •O 3 , S 4 , P 8 -more complex elements •H 2 O, C 12 H 22 O 11 –compounds • Substance consists of two or more elements MOLECULAR COMPOUNDS Compound 1 Molecule Contains HCl 1 H atom & 1 Cl atom H 2 O 2 H atoms & 1 O atom NH 3 1 N atom & 3 H atoms C 3 H 8 3 C atoms & 8 H atoms IONIC COMPOUNDS •Ions are atoms or groups of atoms that possess an electric charge. •Two basic types of ions: Positive ions or cations –Na + , Ca 2+ , Al 3+ –NH 4 + - polyatomic cation Negative ions or anions –F - , O 2- , N 3- –SO 4 2- , PO 4 3- - polyatomic anions FORMULA WEIGHTS (FW) • FW of a substance is the SUM OF THE ATOMIC WEIGHTS OF THE ELEMENTS IN THE CHEMICAL FORMULA , each taken the number of times the element occurs.
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Lec04 Mole Concept - THE MOLE CONCEPT A number of atoms...

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