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Chemical Formulas and Compounds: Naming and Formulas of Binary Ionic and Molecular Compounds

This chapter covers chemical formulas and compounds, focusing on the number of atoms of each kind in formulas, examples of monatomic ions, nomenclature rules for binary ionic compounds, naming and writing formulas for compounds with polyatomic ions, binary molecular compounds, and how to determine oxidation numbers. Includes problems and examples.

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Chemical Formulas and Compounds: Naming and Formulas of Binary Ionic and Molecular Compounds

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  1. Chapter 7 • Chemical Formulas and Chemical Compounds

  2. Chemical Formulas • Number of atoms of each kind • Examples • C8H18 • Al2(SO4)3

  3. Monatomic Ions • Formed by gaining or losing electrons • S-block • +1 or +2 charge • P-Block • Groups 15, 16, 17 • 1-, 2-, or 3- charge • Group 14 • 2+ charge

  4. Monatomic Ions • D-block • 2+, 3+ charge • Sometimes 1+ and 4+ • Nomenclature • Cations • Element’s name • Anion • Ending of name is dropped • Add -ide

  5. Binary Ionic Compounds • Composed of 2 atoms • Neutral compounds • Cation written first • Cross over to balance charge • Name of cation given first • Name of anion given second

  6. Problem • Write the formulas for the binary ionic compounds formed between the following elements • Zinc and iodine • Zinc and sulfur • Potassium and iodine • Magnesium and chlorine • Sodium and sulfur • Aluminum and nitrogen

  7. Problem • Name the binary ionic compounds indicated by the following formulas • AgCl • ZnO • CaBr2 • SrF2 • BaO • CaCl2

  8. Binary Ionic Compounds • Elements that form 2 or more cations • Stock System • Use Roman numerals to indicate ion’s charge • Examples • Fe2+→ Iron(II) • Fe3+→ Iron(III) • CuCl2→ copper(II) chloride

  9. Problem • Write the formula and give the name for the compound formed by the ions • Cr3+ and F- • Cu2+ and Br- • Fe2+ and O2- • Pb2+ and Cl- • Sn2+ and F- • Hg2+ and S2-

  10. Problem • Give the names for the following compounds • CuO • CoF3 • SnI4 • FeS

  11. Polyatomic Ions • Oxyanions • One less oxygen → -ite • One less oxygen than -ite → hypo- • One more oxygen than -ate → per- • ClO- → hypochlorite • ClO2-→ chlorite • ClO3-→ chlorate • ClO4-→ perchlorate

  12. Problem • Write the formula for • tin(IV) sulfate • Lithium nitrate • Copper(II) sulfate • Sodium carbonate • Calcium nitrite • Potassium perchlorate

  13. Problem • Give the names for the following compounds • Ca(OH)2 • KClO3 • NH4OH • FeCrO4 • KClO

  14. Binary Molecular Compounds • 2 nomenclature systems • Stock system • Prefixes • CCl4→ carbon tetrachloride • CO → carbon monoxide • CO2→ carbon dioxide

  15. Prefixes • 1 → mono- • 2 → di- • 3 → tri- • 4 → tetra- • 5 → penta- • 6 → hexa- • 7 → hepta- • 8 → octa- • 9 → nona- • 10 → deca

  16. Rules • Less electronegative element 1st • 2nd element → combine prefix, root, and ending -ide • O or a of prefix is dropped when root starts with vowel • P4O10→ tetraphosphorus decoxide

  17. Problem • Name the following binary molecular compounds • As2O5 • SO3 • ICl3 • PBr5

  18. Problem • Write the formula for • Oxygen difluoride • Carbon tetraiodide • Phosphorus trichloride • Dinitrogen trioxide

  19. Oxidation Numbers • Atoms in pure element → 0 • More electronegative element → negative charge as an anion • Fluorine → -1 • Oxygen → -2 • Exceptions: peroxides → -1 fluoride → +2 • Hydrogen → +1 • Exception: w/metals → -1

  20. Oxidation Numbers • Sum of neutral compound equals 0 • Sum of atoms in polyatomic ion equals charge of ion

  21. Problems • Assign oxidation numbers to each atom in the following compounds or ions: • HF • H2O • UF6 • H2SO4 • ClO3-

  22. Problems • Assign oxidation numbers to each atom in the following compounds or ions: • CF4 • SO2 • P4O10 • HClO3

  23. Oxidation Numbers, Formulas, & Names • Oxidation numbers can be used like ionic charges to determine formulas • Use stock system • Roman numerals show oxidation number • SO2 - sulfur(IV) oxide • SO3 - sulfur(VI) oxide

  24. Problem • Give the name according to the stock system of the following compounds: • PCl3 • N2O • PbO2 • CI4 • As2S3 • NCl3

  25. Problem • Give the formula for the following compounds: • Sodium(I) oxide • Sulfur(II) chloride • Nitrogen(V) oxide • Carbon(IV) sulfide • Phosphorus(III) iodide

  26. Formula & Molar Masses • Molecules and ions have average mass • H2O → 18.02 amu • Numerically equal to molar mass • Mass of one mole of a compound • H2O → 18.02 g/mol

  27. Problems • What is the molar mass of: • KClO3 • H2SO4 • Ca(NO3)2 • Ba(OH)2 • NaNO3 • Al2S3

  28. Conversions • Molar mass is a conversion factor • g/mol • mol/g

  29. Problems • What is the mass in grams of 2.50 mol of oxygen gas? • What is the mass in grams of 0.257 mol of calcium nitrate? • How many moles are in 3.82 g SO2? How many molecules are in this sample of SO2?

  30. Problem • Ibuprofen, C13H18O2, is the active ingredient in many nonprescription pain relievers. Its molar mass is 206.29 g/mol. • If the tablets in a bottle contain a total of 33 g of ibuprofen, how many moles of ibuprofen are in the bottle? • How many molecules of ibuprofen are in the bottle? • What is the total mass in grams of carbon in 33 g of ibuprofen?

  31. Percentage Composition • Percentage by mass of an element in compound • (mass of element)/(mass of compound) x 100 = % element in compound

  32. Problem • Find the percentage composition of copper(I) sulfide, Cu2S. • Calculate the percentage composition of sodium nitrate.

  33. Problem • As some salts crystallize from a water solution, they bind water molecules in their crystal structure. Sodium carbonate forms such a hydrate, in which 10 water molecules are present for every formula unit of sodium carbonate. Find the mass percentage of water in sodium carbonate decahydrate, Na2CO3·10H2O, which has a molar mass of 286.14 g/mol.

  34. Empirical Formulas • Compound with subscripts showing smallest whole-number mole ratio of atoms • BH3 vs. B2H6 • Convert percent composition to mass composition • Convert mass composition to composition in moles

  35. Empirical Formulas • Divide each number of moles by smallest number of moles • Round to nearest whole number

  36. Problem • Quantitative analysis shows that a compound contains 32.38% sodium, 22.65% sulfur, and 44.99% oxygen. Find the empirical formula of this compound.

  37. Problem • Analysis of a 10.150 g sample of a compound known to contain only phosphorus and oxygen indicates a phosphorus content of 4.433 g. What is the empirical formula of this compound?

  38. Molecular Formula • x(empirical formula) = molecular formula • Must know formula mass • (Experimental formula mass)/(Empirical formula mass)

  39. Problem • The empirical formula of a compound of phosphorus and oxygen was found to be P2O5. Experimentation shows that the molar mass of this compound is 283.89 g/mol. What is the compound’s molecular formula?

  40. Problem • Determine the molecular formula of the compound with a empirical formula of CH and a formula mass of 78.110 amu • A sample of a compound with a formula mass of 34.00 amu is found to consist of 0.44 g H and 6.92 g O. Find its molecular formula.

  41. Chapter Review • Pg. 251 • 3abcd, 4bcd, 5de, 6ace, 7bd, 8ab, 10ace, 11cd, 16cd, 23bce, 24bce, 25bde, 28ac, 30bd, 31, 32, 36, 38

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