נושא 3 חלק א' מולקולות, תרכובות, יונים, ונוסחאות 1 Prof. Zvi C. Koren 24.10.07
Examples: Molecular Formula, Moles, Molecules, Atoms: Summary Molecular formula = (CH 3 ) 2 CF 2 1 molecule contains: 3 C atoms 6 H atoms 2 F atoms 100 molecules contain: 300 C atoms 600 H atoms 200 F atoms 1 mole of molecules contains: 3 moles of C atoms = 3 x 6.022 x 10 23 C atoms 6 moles of H atoms = 6 x 6.022 x 10 23 H atoms 2 moles of F atoms = 2 x 6.022 x 10 23 F atoms OK? OK! 2 Prof. Zvi C. Koren 24.10.07
Percent Composition Weight (or mass) % of each element in a compound For example, NH 3 : 14.01 g % N in NH 3 x 100 17.030 g 3 x 1.008 g % H in NH 3 x 100 17.030 g 82.27 17.73 % N % H 100.00 % 3 Prof. Zvi C. Koren 24.10.07
Determining Empirical and Molecular Formulas Given: Percent Compositions: H: 8.20% C: 39.34% O: 52.46% Assume 100 g compound: 1mol H # mol H atoms = 8.20 g 8.13573 mol H 3.27533 = 2.48 x 2 = 4.96 1.0079g H (can round off to nearest integer if < 0.10) 1mol C 12.011g C # mol C atoms = 39.34 g 3.27533 mol C 1mol O # mol O atoms = 52.46 g 3.27887 mol O 15.9994g O Empirical Formula = H 5 C 2 O 2 If MW = 122 g/mol, Molecular Formula =? 3.27533 Empirical Formula Weight 61 g/mol MW = 2 Molecular Formula (H 5 C 2 O 2 ) 2 H 10 C 4 O 4 EW 3.27533= 1.001 x 2 = 2.00 4 Prof. Zvi C. Koren 24.10.07 = 1 x 2 = 2
Empirical Formulas from Combustion Analysis & Law of Conservation of Mass Combustion reaction: H x C y O z + O 2 (g) -----> CO 2 (g) + H 2 O(g) Problem: 0.513 g of compound is burned 0.501 g CO 2 & 0.103 g H 2 O produced. Empirical formula of compound =? Solution: H x C y O z + O 2 (g) CO 2 (g) + H 2 O(g) conservation of C conservation of H g C in comp d = g C in CO 2 = 0.501 g CO 2 1mol CO2 44.010g CO 2 1mol C 1mol CO 2 12.011 g C 1mol C = 0.137 g C g H in comp d = g H in H 2 O = 0.103 g H 2 O 1mol H O 2 2 mol H 1.0079 g H 18.015g H2O 1mol H2O 1mol H = 0.0115 g H g O in comp d = Total g of comp d g C in comp d g H in comp d = 0.365 g O Moles C in comp d = 0.0114 Moles H in comp d = 0.0114 Moles O in comp d = 0.0228 1 1 2 Empirical Formula = HCO 2 If MW = 90.04 g/mol Molecular Formula = H 2 C 2 O 4 (After 3 lessons) 5 Prof. Zvi C. Koren 24.10.07
Molecular Elements The Halogens diatomic molecules 6 Prof. Zvi C. Koren 24.10.07
Carbon Allotropes 7 Prof. Zvi C. Koren 24.10.07
diatomic molecule O 2 light 2 O O + O 2 O 3 triatomic molecule Oxygen Allotropes 8 Prof. Zvi C. Koren 24.10.07
tetrahedral (tetrahedron) tetratomic molecule 9 Prof. Zvi C. Koren 24.10.07
octatomic molecule 10 Prof. Zvi C. Koren 24.10.07
The Language of Chemistry Letters = Element Symbols Words = Compound Formulas 11 Prof. Zvi C. Koren 24.10.07
Compounds Ionic (typically between Metals & Nonmetals) Covalent (between Nonmetals) composed of ions composed of e-sharing positive (+): Cation Electric Glue negative (-): Anion Atoms share the same e-pair A : B Salts & Oxides 12 Prof. Zvi C. Koren 24.10.07
Ionic Compounds composed of ions: positive(+) and negative(-) when Metals meet Nonmetals, they instantly fall in LOVE Metals LOVE to transfer electrons to Nonmetals opposites attract or viva la difference 13 Prof. Zvi C. Koren 24.10.07
Ionic Charges Main Group Number is the number of valence electrons = Number of e s in outermost shell Octet Rule: Atoms combine to mimic the very stable noble elements X Na + Cl Na+ Cl He Ne Ar Examples of compounds: Ca & Br: Ca 2+ + 2Br CaBr 2 (s) Ba & S: Ba 2+ + S 2 BaS(s) Al & O: 2Al 3+ + 3O 2 Al 2 O 3 (s) K & N: 3K + + N 3 K 3 N(s) Typical charges for monatomic ions: 1+ 2+ 3+ 4-3- 2-1- Kr Xe Rn Examples of ions: Na + Mg 2+ Al 3+ C 4- N 3- O 2 - F - 14 Prof. Zvi C. Koren 24.10.07
Charges on Transition Metals Transition Group Number = maximum charge (but lower charges are possible!!!) Sc 3+ Ti 4+ V 5+ Cr 6+ Mn 7+ Fe Cu Ag + only 3+ (After 4 lessons) Os 8+ Au 3+ Note exception 15 Prof. Zvi C. Koren 24.10.07
Ion Fe 2+ Fe 3+ Cu + Cu 2+ Hg 2 2+ Hg 2+ Sn 2+ Sn 4+ Pb 2+ Pb 4+ Roman-Numeral Name Iron(II) ion Iron(III) ion Copper(I) ion Copper(II) ion Mercury(I) ion Mercury(II) ion Tin(II) ion Tin(IV) ion Lead(II) ion Lead(IV) ion Transition Metals & Others (continued) Common Ions with two possible charges -ous and ic Names Ferrous ion Ferric ion Cuprous ion Cupric ion Mercurous ion Mercuric ion Stannous ion Stannic ion Plumbous ion Plumbic ion 16 Prof. Zvi C. Koren 24.10.07 Fe Cu Hg Sn Pb
Elements to Remember 17 Prof. Zvi C. Koren 24.10.07
Nomenclature of Ionic Compounds )מינוח, כיניון, שיטת כינוי( Cation: Metal = Element name or NH 4+ = ammonium ion (and its derivatives: CH 3 NH 3+, ) polyatomic cation Anion: Monatomic = Element root name + ide 4A C 4 carbide 5A N 3 nitride P 3 phosphide 18 Prof. Zvi C. Koren 24.10.07 6A O 2 oxide S 2 sulfide Examples: Se 2 selenide CaBr 2 calcium bromide BaS barium sulfide Te 2 telluride Al 2 O 3 aluminum oxide K 3 N potassium nitride FeCl 2 iron(ii) chloride = ferrous chloride FeCl 3 iron(iii) chloride = ferric chloride Hg 2 Cl 2 mercury(i) chloride = mercurous chloride HgCl 2 mercury(ii) chloride = mercuric chloride LiH lithium hydride (NH 4 ) 3 P ammonium phosphide 7A H hydride F fluoride Cl chloride Br bromide I iodide