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Chapter 7 Chemical Formulas & Chemical Compounds

Chapter 7 Chemical Formulas & Chemical Compounds. 7.1 Chemical Names & Formulas. Ions. Cation : A positive ion Mg 2+ , NH 4 + Anion : A negative ion Cl - , SO 4 2 - Ionic Bonding : Force of attraction between oppositely charged ions. Predicting Ionic Charges. Groups 3 - 12 :.

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Chapter 7 Chemical Formulas & Chemical Compounds

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  1. Chapter 7Chemical Formulas &Chemical Compounds 7.1 Chemical Names & Formulas

  2. Ions • Cation: A positive ion • Mg2+, NH4+ • Anion: A negative ion • Cl-, SO42- • Ionic Bonding: Force of attraction between oppositely charged ions.

  3. Predicting Ionic Charges Groups 3 - 12: Many transition elements have more than one possible oxidation state. Iron (II) = Fe2+ Iron (III) = Fe3+

  4. Predicting Ionic Charges Groups 3 - 12: Some transition elements have only one possible oxidation state. Zinc = Zn2+ Silver = Ag1+

  5. Magnesium Bromide Mg+ 2 Br – 1 Mg1Br2 MgBr2 Calcium Sulfide Ca + 2 S – 2 Ca2S2 CaS Formula Writing for Binary Ionic Compounds criss-cross the oxidation numbers to balance out the charge.

  6. Writing Ionic Compound Formulas Example: Iron (III) chloride 1. Write the formulas for the cation and anion, including CHARGES! Fe3+ Cl- 2. Check to see if charges are balanced. 3 3. Balance charges, if necessary, using subscripts. Not balanced!

  7. Naming Ionic Compounds 1. Cation first, then anion 2. Monatomic cation = name of the element • Ca2+ = calciumion 3. Monatomic anion = root + -ide • Cl- = chloride • CaCl2= calcium chloride

  8. Naming Ionic Compounds Metals with multiple oxidation states • some metal forms more than one cation • use Roman numeralin name • PbCl2 • Pb2+is cation • PbCl2 = lead (II) chloride

  9. Elements with Multiple Oxidation Numbers Manganese II Mn+2 Manganese III Mn+3 Manganese VII Mn+7 Cobalt II Co+2 Cobalt III Co+3 Gold I Au+1 Gold III Au+3 Nickel II Ni+2 Nickel III Ni+3 Nickel IV Ni+4 **Silver Ag+1 **Zinc Zn+2 **Cadmium Cd+2 Copper I Cu+1 Copper II Cu+2 Iron II Fe+2 Iron III Fe+3 Mercury I Hg+1 Mercury II Hg+2 Lead II Pb+2 Lead IV Pb+4 Tin II Sn+2 Tin IV Sn+4 Chromium II Cr+2 Chromium III Cr+3 Chromium VI Cr+6

  10. ♥ Poly Atomic Ions to Know and Love ♥ Name Formula Name Formula

  11. ♥ More Poly Atomic Ions to Know and Love ♥ Name Formula Name Formula

  12. Naming Compounds with Polyatomic Ions Formula Name • (NH4)2SO4 ammonium sulfate • ZnCO3 zinc carbonate • NH4Br ammonium bromide • Li2CO3 lithium carbonate * Polyatomic & monatomic cation names remain the same, monatomic anions change their ending to –ide.

  13. Writing Ionic Compound Formulas Example: Barium nitrate Ba2+ ( ) NO3- 2 1. Write the formulas for the cation and anion, including CHARGES! Not balanced! 2. Check to see if charges are balanced. 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.

  14. Writing Ionic Compound Formulas Example: Ammonium sulfate ( ) NH4+ SO42- 2 1. Write the formulas for the cation and anion, including CHARGES! Not balanced! 2. Check to see if charges are balanced. 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.

  15. Writing Ionic Compound Formulas Example: Aluminum sulfide Al3+ S2- 2 3 1. Write the formulas for the cation and anion, including CHARGES! Not balanced! 2. Check to see if charges are balanced. 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.

  16. Writing Ionic Compound Formulas Example: Magnesium carbonate Mg2+ CO32- 1. Write the formulas for the cation and anion, including CHARGES! 2. Check to see if charges are balanced. They are balanced! 3. Simplify to a formula unit.

  17. Writing Ionic Compound Formulas Example: Zinc hydroxide Zn2+ ( ) OH- 2 1. Write the formulas for the cation and anion, including CHARGES! Not balanced! 2. Check to see if charges are balanced. 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.

  18. Writing Ionic Compound Formulas Example: Aluminum phosphate Al3+ PO43- 1. Write the formulas for the cation and anion, including CHARGES! They ARE balanced! 2. Check to see if charges are balanced.

  19. Cr2O3 Cr2O CuSO4 Ni(OH)2 Cr2(C2O4)3 Cu2S CuS chromium (III) oxide chromium (I) oxide copper (II) sulfate nickel (II) hydroxide chromium (III) oxalate copper (I) sulfide copper (II) sulfide More Examples… Chemical Formula Chemical Name

  20. Hydrates • Hydrate – when a water molecule (s) are chemically bonded to the ionic compound. • Normal ionic naming protocol are used, then followed by the word “hydrate.” • Prefixes are added to indicate the number of water molecules when naming hydrates.

  21. Hydrate Prefixes

  22. Hydrates • Example: MgBr2∙ 6H2O Magnesium bromide hexahydrate • The “ ∙ ” means “loosely bonded” • Hygroscopic - easily absorb water molecules from the air. • Deliquescent- very hygroscopic; takes out water from the air to dissolve completely to form a liquid solution. • Anhydrous – when all of the water has been removed.

  23. Naming Binary Covalent Compounds • Compounds between two nonmetals • First element in the formula is named first. • Second element is named as if it were an anion. • Use prefixes • Only use mono on second element diphosphorus pentoxide P2O5 = CO2 = carbon dioxide CO = carbon monoxide N2O = dinitrogen monoxide

  24. Acids • Acids always begin with Hydrogen

  25. Bases

  26. Organic Compounds • Organic compounds are named using a different set of rules. • The simplest group is the hydrocarbons. These compounds are composed solely of the elements carbon and hydrogen. • Carbon atoms can link to each other in chains and in rings.

  27. Naming Hydrocarbons • The stem of the compound name is then chosen from the following table:

  28. Hydrocarbons: Alkanes • These molecules have the generic formula: CnH2n+2 • They contain all single bonds.

  29. Hydrocarbons: Alkenes • These molecules have the generic formula: CnH2n • They contain double bonds between carbon atoms.

  30. Hydrocarbons: Alkynes • These molecules have the generic formula: CnHn • They contain triple bonds between carbon atoms.

  31. Chapter 7Chemical Formulas &Chemical Compounds 7.2 Oxidation Numbers

  32. Oxidation Numbers • Oxidation Number – numbers assigned to atoms composing a compound or ion that indicate the general distribution of electrons among bonded atoms

  33. Chapter 7Chemical Formulas &Chemical Compounds 7.3 Using Chemical Formulas

  34. Molar Mass • The mass of 1 mole of a pure substance is called its Molar Mass. • Ex: Molar mass of Iron is 55.847 g/mol What is the molar mass of Platinum? 195.08 g/mol

  35. Molar Mass • The molar mass depends on the particles that compose the compound. If your element exists as a molecule, i.e. BrINClHOF, one mole of these particles contains 2 moles of the element as an atom. • Determine the molar mass of oxygen molecules (O2) (16.00 g/mol) x (2 atoms) = 32.00 g/mol The molar mass of oxygen molecules (O2) is twice the molar mass of oxygen atoms!

  36. Formula Mass • The molar mass of a compound is the mass of the atomic mass units of one molecule. • This takes into consideration the number of atoms of each element in a compound. • Formula Mass is calculated the same way as molar mass except it is measured in amu, instead of g/mol.

  37. Calculating Formula Mass Calculate the formula mass of magnesium carbonate, MgCO3. 24.31 + 12.01 + 3(16.00) = 84.32 amu

  38. Steps for Calculating Molar Mass for Compounds • List the elements • Determine how many atoms of each • Identify the atomic masses from the periodic table • Multiply how many atoms by the respective atomic mass • Add up the totals for the Molar Mass

  39. Practice • NaCl • Na 1 x 22.9 = 22.9 • Cl 1 x 35.45 = 35.45 • 58.35 • H2O H 2 x 1.008 = 2.016 O 1 x 15.99 = 15.99 18.006 g/mol g/mol • K2O • K 2 x 39.1 = 78.2 • O 1 x 15.99 = 15.99 • 94.19 • C6H12O6 • C 6 x 12.01 = 72.06 • H 12 x 1.008 = 12.096 • O 6 x 15.99 = 95.94 • 180.096 g/mol g/mol

  40. Calculating Percentage Composition Calculate the percentage composition of magnesium carbonate, MgCO3. 24.31 + 12.01 + 3(16.00) = 84.32 amu 100.00

  41. Mass Percent • So…. In one mole of H2O, how many grams of Hydrogen are there? 2 mol H x 1.008g H = 2.016 g H in 1 mol H2O 1 mol H • What % of Hydrogen, by mass, is in H2O? 2.016 g H x 100 = 11.2 % H 18 g H20 *Must also find molar mass of H2O What % of Oxygen, by mass is in H2O?

  42. Formulas Empirical formula: the lowest whole number ratio of atoms in a compound. • molecular formula = (empirical formula)n [n = integer] • molecular formula = C6H6 = (CH)6 • empirical formula = CH Molecular formula: the true number of atoms of each element in the formula of a compound.

  43. Formulas Formulas for ionic compounds are ALWAYS empirical (lowest whole number ratio). Often, these are called formula units. Examples: NaCl MgCl2 Al2(SO4)3 K2CO3

  44. Formulas Formulas for molecular compoundsMIGHT be empirical (lowest whole number ratio). Molecular: C6H12O6 H2O C12H22O11 Empirical: H2O CH2O C12H22O11

  45. Chapter 7Chemical Formulas &Chemical Compounds 7.4 Determining Chemical Formulas

  46. Empirical Formula Determination • Base calculation on assumption of 100 grams of compound. • Determine moles of each element in 100 grams of compound. • Divide each value of moles by the smallest of the values. • Multiply each number by an integer to obtain all whole numbers.

  47. Empirical Formula Determination Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula of adipic acid?

  48. Empirical Formula Determination(part 2) Divide each value of moles by the smallest of the values. Carbon: Hydrogen: Oxygen:

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