You are experts at knowing the symbols of elements and using these symbols to write formulae. Now we are going to use these concepts to describe chemical changes substances undergo. (aka chemical reactions) A chemical reaction is the process by which one or more substances are changed into one or more DIFFERENT substances.

Bonds are broken and new bonds are formed, in other words, atoms are rearranged. A chemical reaction is represented by a chemical equation, which is a shorthand method of saying what happens in a chemical reaction. An equation shows two things: 1.The change that takes place. 2.Relative amounts of the various elements and compounds that take part in these changes.

NOTATION: REACTANTS YIELD PRODUCTS 2 C 2 H 2(g) + 5 O 2(g) 4 CO 2(g) + 2 H 2 O (g) s = solid g = gas l = liquid cr = crystallineaq = aqueous

To balance equations: Determine the reactants and products from the problem. Assemble the equation.( +and ) YOU MUST WRITE CORRECT FORMULAS!!!!! Balance the equation, according to the law of conservation of mass. All atoms must be present and accounted for, NO A.W.O.L.’s.

Rules: 1.Remember the seven diatomic elements. 2.Change only the coefficients, never the subscripts. Hints: Balance “lone” elements last. If a polyatomic ion is represented in both the products and reactants, balance the entire quantity and not each single atom. If OH 1- and H 1+ on one side of the equation and H 2 O on the other, change the formula of water to its structural formula H OH and balance the H and OH separately.

In the combustion of hydrocarbons (compound containing C and H) begin balancing by placing a 2 in front of the hydrocarbon. One final note: It is okay to use fractional coefficients, though it is NOT PREFERRED, as long as they do not split atoms. Coefficients should be reduced if possible.

There are hundreds of different kinds of chemical reactions, but many can be divided into 5 general categories. Once we know the type of reaction, we can then predict the products of the reaction.

General Form:A + X AX Combination of 2 elements to form a binary compound Metal and nonmetal ONLY ONE PRODUCT Tarnishing of silversilver reacts with sulfur Ag (s) + S (s) Ag 2 S (s) 2 binary ionic compound (salt)

General Form:A + X AX Combination of 2 elements to form a binary compound Metal and nonmetal Copper-bottomed potscopper reacts with oxygen Cu (s) + O 2(g) CuO (s) 2 binary ionic compound (salt) Cu (s) + O 2(g) Cu 2 O (s) 4 2 2

General Form:A + X AX Combination of 2 elements to form a binary compound Metal and nonmetal Rusting (oxidation of iron) iron reacts with oxygen Fe (s) + O 2(g) FeO (s) 2 binary ionic compound (salt) Fe (s) + O 2(g) Fe 2 O 3(s) H2OH2O H2OH2O

General Form:A + X AX Combination of 2 elements to form a binary compound Nonmetal and nonmetal ONLY ONE PRODUCT For the negative charge, pick the element with the greatest electronegativity (closest to Fluorine) binary covalent compound (molecule) For the positive charge(s), determine the number of electrons to lose the p sublevel AND the number of electrons to lose the s and p sublevel

General Form:A + X AX Combination of 2 elements to form a binary compound Nonmetal and nonmetal binary covalent compound (molecule) Burning sulfursulfur reacts with oxygen S (s) + O 2(g) SO 2(g) S (s) + O 2(g) SO 3(g) 2 2 3

General Form:A + X AX Combination of 2 elements to form a binary compound Nonmetal and nonmetal binary covalent compound (molecule) Liquid bromine and gaseous chlorine Br 2(l) + Cl 2(g) BrCl 5(l) 2 5 Br 2(l) + Cl 2(g) BrCl 7(l) 2 7

General Form:A + X AX Combination of 2 compounds Metallic oxide and Nonmetallic oxide ONLY ONE PRODUCT The nonmetallic oxide determines the polyatomic ion If the non-metal’s charge is “the higher charge” = -ate If the non-metal’s charge is “the lower charge” = -ite Ternary ionic compound (salt with polyatomic ion) To determine the overall formula, bond the metallic ion with the polyatomic ion.

General Form:A + X AX Combination of 2 compounds Metallic oxide and Nonmetallic oxide Ternary ionic compound (salt with polyatomic ion) Li 2 O (s) + CO 2(g) Li 2 CO 3(s) CaO (s) + SiO 2(s) CaSiO 3(s)

General Form:A + X AX Combination of 2 compounds Metallic oxide and WATER BASE (metal with OH 1- ) CaO (s) + H 2 O (l) Ca(OH) 2(aq) Na 2 O (s) + H 2 O (l) NaOH (aq) 2

General Form:A + X AX Combination of 2 compounds Nonmetallic oxide and WATER OXYACID (H 1+ and polyatomic ion) The nonmetallic oxide determines the polyatomic ion If the non-metal’s charge is “the higher charge” = -ate If the non-metal’s charge is “the lower charge” = -ite To determine the overall formula, bond the hydrogen ion with the polyatomic ion.

General Form:A + X AX Combination of 2 compounds OXYACID (H 1+ and polyatomic ion) CO 2(s) + H 2 O (l) H 2 CO 3 (aq) SO 3(s) + H 2 O (l) H 2 SO 4 (aq) Nonmetallic oxide and WATER OXYACID (H 1+ and polyatomic ion) OXYACID (H 1+ and polyatomic ion) Nonmetallic oxide and WATER OXYACID (H 1+ and polyatomic ion)

Acid AnhydrideAcid CO 2 + H 2 OH 2 CO 3 N 2 O 3 + H 2 O2 HNO 2 N 2 O 5 + H 2 O2 HNO 3 P 2 O H 2 O2 H 3 PO 3 P 2 O H 2 O2 H 3 PO 4 SO 2 + H 2 OH 2 SO 3 SO 3 + H 2 OH 2 SO 4

General Form:AX A + X Decomposition of a binary compound into 2 elements ELECTROLYTIC DECOMPOSITION Industrial production of metals Water ONLY ONE REACTANT H 2(g) + O 2(g) H 2 O (l) 2 e-e- 2 Molten Binary Salt Mg (s) + Cl 2(g) MgCl 2(l) e-e-

General Form:AX A + X Decomposition of a binary compound into 2 elements THERMAL DECOMPOSITION (heat) ONLY ONE REACTANT KCl (s) + O 2(g) KClO 3(s) 2 2 Metallic Chlorate Metallic chloride + oxygen 3

General Form:AX A + X Decomposition of a binary compound into 2 elements THERMAL DECOMPOSITION (heat) ONLY ONE REACTANT BaO (s) + CO 2(g) BaCO 3(s) Metallic Carbonate Metallic oxide + carbon dioxide CaO (s) + CO 2(g) CaCO 3(s)

General Form:AX A + X Decomposition of a binary compound into 2 elements THERMAL DECOMPOSITION (heat) ONLY ONE REACTANT Na 2 CO 3(s) + H 2 O (g) + CO 2(g) NaHCO 3(s) Metallic Bicarbonate Metallic carbonate + water + carbon dioxide 2

General Form:AX A + X Decomposition of a binary compound into 2 elements THERMAL DECOMPOSITION (heat) ONLY ONE REACTANT CaO (s) + H 2 O (g) Ca(OH) 2(s) Metallic Hydroxide Metallic oxide + water Base Na 2 O (s) + H 2 O (g) NaOH (s) 2

General Form:AX A + X Decomposition of a binary compound into 2 elements THERMAL DECOMPOSITION (heat) ONLY ONE REACTANT CO 2(g) + H 2 O (l) H 2 CO 3(aq) Oxyacids Nonmetallic oxide + water SO 2(g) + H 2 O (l) H 2 SO 3(aq) SO 3(g) + H 2 O (l) H 2 SO 4(aq)

General Form:AX A + X Decomposition of a binary compound into 2 elements THERMAL DECOMPOSITION (heat) ONLY ONE REACTANT Hg (l) + O 2(g) HgO (s) Metallic Oxides Metal + oxygen 22

General Form:A + BX AX + B Element + Compound If free element in the reactants forms cations, then it will replace the positive ion in the compound. If free element in the reactants forms anions, then it will replace the negative ion in the compound.

General Form:A + BX AX + B Element + Compound Al (s) + Fe 2 O 3(s) 2 Fe (l) + Al 2 O 3(s) 2 Cl 2(g) + KBr (s) 2 KCl (s) + Br 2(l) 2

General Form:AX + BY AY + BX Compound + Compound Cmpd + Cmpd

General Form:AX + BY AY + BX Compound + Compound Cmpd + Cmpd AgNO 3(aq) + NaCl (aq) AgCl (s) + NaNO 3(aq)

General Form:AX + BY AY + BX Compound + Compound Cmpd + Cmpd H 2 SO 4(aq) + Na 2 CO 3(aq) Na 2 SO 4(aq) + H 2 CO 3(aq) H 2 SO 4(aq) + Na 2 CO 3(aq) Na 2 SO 4(aq) + H 2 O (l) + CO 2(g)

General Form:AX + BY AY + BX Compound + Compound Cmpd + Cmpd HCl (aq) + Na 2 SO 3(aq) NaCl (aq) + H 2 SO 3(aq) HCl (aq) + Na 2 SO 3(aq) NaCl (aq) + H 2 O (l) + SO 2(g) 2 2

General Form:AX + BY AY + BX Compound + Compound Cmpd + Cmpd NH 4 Cl (s) + NaOH (aq) NaCl (aq) + NH 4 OH (aq) NH 4 Cl (s) + NaOH (aq) NaCl (aq) + H 2 O (l) + NH 3(g)

General Form:AX + BY AY + BX Compound + Compound Cmpd + Cmpd NaCl (s) + H 2 SO 4(aq) HCl (g) + Na 2 SO 4(aq) 2 2 FeS (s) + HCl (aq) H 2 S (g) + FeCl 2(aq) 2

General Form:AX + BY AY + BX Compound + Compound Cmpd + Cmpd HCl (aq) + NaOH (aq) NaCl (aq) + H 2 O (l)

HCl (aq) + NaOH (aq) NaCl (aq) + H 2 O (l)

HCl (aq) + NaOH (aq) NaCl (aq) + H 2 O (l) H 1+ (aq) + Cl 1- (aq) + Na 1+ (aq) + OH 1- (aq) Na 1+ (aq) + Cl 1- (aq) + H 2 O (l)

H 1+ (aq) + Cl 1- (aq) + Na 1+ (aq) + OH 1- (aq) Na 1+ (aq) + Cl 1- (aq) + H 2 O (l) H 1+ (aq) + OH 1- (aq) H 2 O (l)

Strong Acids are to be dissociated, while weak ones are not Binary:HCl,HBr, HI,HF is weak Ternary:The number of oxygen exceeds the hydrogen atoms by two or more. StrongWeak HClHCN HClO 3 HClO HClO 4 HC 2 H 3 O 2 H 2 SO 4 H 2 SO 3 HNO 3 HNO 2 H 2 SeO 4 H2CO3H2CO3

Strong Bases dissociate (hydroxides), weak ones do not Salts dissociate if soluble; if not leave undissociated. Oxides are either solids or gases; therefore do not dissociate. StrongWeak NaOHNH 3

Neutralization is a common form of a metathesis reaction that produces water. HNO 3(aq) + KOH (aq) KNO 3(aq) + H 2 O (l) Acid + Base Binary/ternary salt + water HCl (aq) + NaOH (aq) NaCl (aq) + H 2 O (l)

The general definition of a combustion reaction is one in which oxygen is a reactant. Specifically, when oxygen reacts with a hydrocarbon to produce carbon dioxide and water. CH 4(g) + O 2(g) CO 2(g) + H 2 O (g) Hydrocarbon and oxygen Carbon dioxide and water 22 C 8 H 18(g) + O 2(g) CO 2(g) + H 2 O (g)

The general definition of a combustion reaction is one in which oxygen is a reactant. Specifically, when oxygen reacts with a hydrocarbon to produce carbon dioxide and water. Hydrocarbon and oxygen Carbon dioxide and water

The general definition of a combustion reaction is one in which oxygen is a reactant. Specifically, when oxygen reacts with a hydrocarbon to produce carbon dioxide and water. Hydrocarbon and oxygen Carbon dioxide and water Hydrocarbon and oxygen Carbon monoxide and water