FORMULA WRITING NAMING EQUATIONS & BALANCING

1. FORMULA WRITINGNAMINGEQUATIONS & BALANCING Kenneth E. Schnobrich

2. Oxidation States & Rules • Oxidation states can represent the loss and gain of electrons or the partial loss and gain of electrons when they are shared unequally. • There are some rules that we follow when assigning oxidation states to the elements represented in the formula • When an element is in its elemental state (uncombined with a different element) it has an assigned oxidation state of 0.

3. Rules • The metals in Group 1 all have assigned oxidation states of +1 in compounds. • The metals in Group 2 all have assigned oxidation states of +2 in compounds. • Hydrogen, in compounds generally has an oxidation state of +1. • Exception - a group of compounds called Hydrides (when hydrogen is combined with metals from Groups 1 & 2, B, and Al). In this case it has an oxidation state of -1 because of its higher electronegativity • NaH (sodium hydride), CaH2 (calcium hydride)

4. Rules • Oxygen has an assigned oxidation of -2 in most compounds because of its high electronegativity. • Exception - In a group of compounds called Peroxides it has an assigned oxidation state of -1. The term Peroxide generally means one more oxygen than normally found. • H2O2 (hydrogen peroxide) and Na2O2 (sodium peroxide) are examples. • Exception - when oxygen combines with fluorine it has an assigned oxidation state of +2. • OF2 - because fluorine is more electronegative • Fluorine and most of the other halogens have assigned oxidation states of -1 in binary compounds. This is due to their electronegativities and the need to gain electrons to complete the octet in the outer energy level.

5. Rules • In Polyatomic Ions the sum of the oxidation states must equal the charge on the ion (see table E). • In the SO4-2 ion (sulfate ion) - sulfur is a +6 and O is a -2 • 1S(+6) + 4O(-2) = (+6) + (-8) = -2 (the charge on the ion) • In Compounds the sum of the oxidation states must always equal 0 because compounds are electrically neutral. • In Al2(SO4)3 (aluminum sulfate) - Al is +3; S is +6; and O is -2 • 2Al(+6) + 3S(+6) + 12O(-2) = (+6) + (+18) + (-24) = 0

6. Let’s Practice • For the following polyatomic ions determine the oxidation state of the underlined element: • ClO3-1 (chlorate ion) • MnO4-1 (permanganate ion) • MnO4-2 (manganate ion) • NO3-1 (nitrate ion) • NO2-1 (nitrite ion) • PO4-3 (phosphate ion)

7. Let’s Practice • For the following compounds determine the oxidation state of the underlined element: • K2SO4 • CaMnO4 • Be3(PO4)2 • LiClO4 • CrCl3 • Na2SO3 • NiBr2

8. Writing a Formula • It is important for you to remember that when you are talking about compounds the sum of the oxidation states must always equal 0. • We will generally divide compounds into four major categories: • Salts • Acids • Bases • Other Molecular Compounds (organic compounds generally) • Compounds can also be divided into binary and ternary compounds.

9. Let’s Make Some Distinctions • Binary Compounds - consist of two different elements combined in different ratios. • Note - some ternary compounds are named like binary compounds • Ternary Compounds - consist of three or moredifferent elements combined in different ratios. • Salts - both binary and ternary are combinations of metals and nonmetals (or nonmetal polyatomic ion). • Acids - both binary and ternary are combinations of nonmetals atoms and are generally identified by “starting with the element hydrogen (H)”.

10. Let’s Make Some Distinctions • Bases - are generally combinations of metals and the nonmetal polyatomic ion OH-1 (hydroxide ion).

11. Now Let’s Write Formulas • We will write formulas by categories to help you differentiate. • Binary Salts - S-2 Na+1 Combined with Na2+1 S-2 Swaping oxidation states method 2(+1) + (-2) = 0 You can also use the lowest common multiple method

12. Now Let’s Write Formulas • We will write formulas by categories to help you differentiate. • Ternary Salts - SO4-2 Al+3 Combined with Al2+3 (SO4)3-2 Swaping oxidation states method 2(+3) + 3(-2) = 0 You can also use the lowest common multiple method

13. Now It’s Your Turn • Write correct formulae for each of the following combinations: • Ca+2 and F-1 • Al+3 and NO3-1 • Li+1 and O-2 • Ba+2 and PO4-3 • NH4+1and S-2 • Ni+3 and ClO2-1 • Cs+1 and N-3 Identify each of these as a binary or ternary compound.

14. Now It’s Your Turn • Write correct formulae for each of the following combinations: • Ca+2 and OH-1 • H+1 and NO3-1 • Li+1 and OH -1 • H+1 and PO4-3 • H+1 and S-2 • Ni+3 and OH-1 • Cs+1 and SCN-1 Identify each of these as an acid, base, or salt.

15. Now Let’s Name • The fancy name for naming is of course nomenclature. We will use the same classifications that we used for formulas. • Binary Salts • Ternary salts • Binary Acids • Ternary acids • Bases • Other compounds

16. Binary Salts • For metals and nonmetals with multiple positive oxidation states we use the “Stock System”. • Check your periodic table and the written formula to determine the positive (+) oxidation state. When there is more than one you must indicate that by using a Roman Numeral in the name enclosed in parenthesisafter the name of the metal or nonmetal. • If there is only one indicate positive oxidation state you do not have to do this

17. Binary Salts (Examples) • Naming follows the sequence - Metal (Roman Numeral if necessary) and nonmetal with the suffix “ide”. • NaCl = sodium chloride • K2S = potassium sulfide • CrF3 = chromium(III) fluoride • ZnO = zinc oxide • KCN = potassium cyanide* • PbI2 = lead(II)iodide *There are some ternary compounds named like binary compounds

18. Ternary Salts (Examples) • Naming follows the sequence - Metal (Roman Numeral if necessary) and nonmetal polyatomic ion name. • NaClO4 = sodium perchlorate • K2SO4 = potassium sulfate • Cr(NO3)3 = chromium(III)nitrate • Zn3(PO4)2 = zinc phosphate • NH4NO3 = ammonium nitrate • PbCrO4 = lead(II)chromate • Co(SCN)2 = cobalt(II)thiocyanate

19. Naming Binary Acids • For the naming of binary acids the rules are relatively simple. It will always be a combination of hydrogen (H) and some other nonmetal. • Binary acids start with the prefix “hydro” and end with the suffix “ic”. The root of the name comes from the nonmetal. • Example: HCl = hydrochloric acid

20. Name These Binary Acidsin Aqueous Solutions • Remember - hydro_______ic • The root is always the name of the anion like “chlor” from chlorine (drop after the last consonant). • HF • HBr • HI • H2S • HCN* • HCl If the substance is in its gaseous state it is named like a normal binary compound (I.e. HCl = hydrogen chloride)

21. Naming Ternary Acids • While there are 3 or more elements the naming is simple. The name comes from the anion in the formula. • If the anion ends in “ate” the acid will end in “ic” • If the anion ends in “ite” the acid will end in “ous” • If there is a prefix associated with the anion it is retained(like - “di”, “per”, “hypo”). • Examples: H2SO4 - contains the “sulfate” ion so it would be named sulfuric acid || H2Cr2O7 - contains the “dichromate” ion so it would be nameddichromic acid

22. Name These Ternary Acids • H3PO4 • HNO3 • HNO2 • HClO • HClO2 • HClO4 • HMnO4 • H2SO3 Please note: Many times there are comparable acids for elements in the same group - like H2SeO4, HBrO, HIO4, H3AsO4

23. Naming Bases (Easy) • The name of the base comes from the name of the metal cation and then the “hydroxide” ion. • NaOH sodium hydroxide • Ba(OH)2 barium hydroxide • Co(OH)3 cobalt (III) hydroxide • Al(OH)3 aluminum hydroxide • Fe(OH)2 iron (II) hydroxide • Pb(OH)4 lead (IV) hydroxide

24. Fill-in the Blanks

25. The Other Compounds • There are compounds that do not fall into the categories we have talked about already. They are generally combinations of nonmetals and in this case the nonmetal assigned a positive (+) oxidation state many times uses the STOCK SYSTEM of naming (the use of the Roman Numeral to indicate the oxidation state. • For Example: CO2 - the common name is carbon dioxide. The STOCK name is carbon (IV) oxide because carbon is showing a +4 oxidation state in the compound. • On the next slide we will illustrate why C is assigned a +4 oxidation state.

26. Why Carbon is a +4Carbon (IV) Oxide - - CO2 C O O EN = 3.5 EN = 3.5 EN = 2.6 Carbon is losing partial control of its 4 valence electrons

27. Name These Compounds Remember to determine the oxidation state of the nonmetal with a positive oxidation state - use the rules you learned. • CO • SO2 • PCl5 • SO3 • N2O5 • NO2 • NCl3

28. Reaction Types • You should be able to indentify the following types of reactions: • Combination or Synthesis Reaction • Decomposition or Analysis Reaction • Single Replacement Reaction • Double Replacement Reaction • Combustion Reactions • Complete • Incomplete

29. Combination (Synthesis) • In a combination reaction usually two elements combine to form a compound. 2Na(s) + Cl2(g) = 2NaCl(s) • To balance the equation you must remember the Law of Conservation of Matter (# of atoms of each element must be the same on both sides of the reaction). • Note: You can only place coefficients in front of the given species never in the middle of a formula.

30. Combination (Synthesis) • Complete the following combination reactions by balancing them: N2(g) + H2(g) = NH3(g) Al(s) + O2(g) = Al2O3(s) S(s) + O2(g) = SO3(g)

31. Decomposition (Analysis) • More complex compounds breakdown into simpler substances or elements. CaCO3(s) = CaO(s) + CO2(g) • Notice in this case the equation is already balanced, this will not always be the case.

32. Decomposition (Analysis) • Balance the following decomposition reactions: HI(g) = H2(g) + I2(g) N2O5(g) = N2(g) + O2(g) KClO3(s) = KCl(s) + O2(g)

33. Single Replacement • In a single replacement reaction one of the species in a formula is replaced by another species: 2NaBr(aq) + Cl2(g) = 2NaCl(aq) + Br2(l) Mg(s) + 2HCl(aq) = MgCl2(aq) + H2(g) Single replacement Single replacement

34. Single Replacement • Balance the following single replacement reactions: Cu(s) + AgNO3(aq)= Cu(NO3)2(aq) + Ag(s) Zn(s) + HCl(aq) = ZnCl2(aq) + H2(g) Zn(s) + H2SO4(aq) = ZnSO4(aq) + H2(g)

35. Double Replacement • In a double replacement reaction the species simply exchange places: AgNO3(aq) + NaCl(aq) = AgCl(s) + NaNO3(aq) In this case, when we check both sides of the equation we find that there is no need to adjust the coefficients - it is balanced

36. Double Replacement • Balance the following double replacement reactions: Ba(NO3)2(aq) + K2SO4(aq) = BaSO4(s) + KNO3(aq) Al(NO3)3(aq) + KOH(aq) = Al(OH)3(s) + KNO3(aq) Cd(NO3)2(aq) + H2S(g) = CdS(s) + HNO3(aq)

37. Combustion Reactions • Complete combustion generally involves the burning of an organic compound in oxygen to form carbon (IV) oxide and water as products: CH4(g) + 2O2(g) = CO2(g) + 2H2O(g)

38. Combustion Reactions • Incomplete combustion reactions generally involve the formation of carbon (II) oxide and water as products: 2CH4(g) + 3O2(g) = 2CO(g) + 4H2O(g)