Chemical Equations Reactions Indications of a Chemical Reaction

Chemical Equations & Reactions

Indications of a Chemical Reaction • Evolution of heat/light • Exothermic and Endothermic • Production of a gas • Formation of a precipitate • Solid that is produced and separates • Color change • Fireworks video (6 min) • Overview of chemical reactions (2 min)

Factors Influencing Rate of Reaction • • • Nature of reactants Surface area Temperature Concentration Catalyst • Increased surface area

Chemical Equations • Chemical Equation = represents, with symbols and formulas, the identities and relative amounts of reactants and products • Reactants (R) – left of arrow • Products (P) – right of arrow

Symbols used in Equations • • - yields - reversible reaction - gaseous product – solid product (g) – gaseous reactant or product (s) – solid reactant or product (l) – liquid reactant or product (aq) – aqueous (dissolved in water)

Writing Chemical Equations 1. Must have correct formulas for each R and P • Don’t forget diatomic elements Br 2, I 2, N 2, Cl 2, H 2, O 2, F 2 2. Law of Conservation of Mass must be satisfied • Balance the equation with coefficients

Translating Equations Write the balanced chemical equations: 1. Calcium phosphate and iron(II) oxide are produced from the reaction of calcium oxide and iron(II) phosphate. 2. The reaction of zinc with aqueous hydrochloric acid produces a solution of zinc chloride and hydrogen gas.

Types of Chemical Reactions • • • Synthesis Decomposition Single Replacement Double Replacement Combustion

Synthesis Reaction • Two or more substances combine to form one product • EX: Calcium + oxygen → ? ? • EX: Barium + chlorine → ? ?

Decomposition Reaction • Single compound breaks down into several simpler substances • There are 4 types of decomposition reactions

Binary Decomposition • Metal oxide → metal + oxygen gas • EX: Zinc oxide → ? ? • Decomposition of nitrogen triiodide

Metal Carbonate Decomposition • Metal carbonate → metal oxide + carbon dioxide • EX: Strontium carbonate → ? ?

Metal Chlorate Decomposition • Metal chlorate → metal chloride and oxygen gas • EX: Iron (III) chlorate → ? ? • EX: Potassium hypochlorite → ? ?

Metal Hydroxide Decomposition • Metal hydroxide → metal oxide + water • EX: Calcium hydroxide → ? ?

Single Replacement • One metal replaces a metal in another compound OR • One nonmetal replaces a nonmetal in another compound EX: Copper + silver nitrate ? ? EX: Calcium chloride + fluorine gas ? ? Thermite

Will a SR reaction always occur? ? • Check the Activity Series • The more reactive element will make a bond. If the more reactive element is already bonded, write NR for no reaction. • EX: Silver + copper (I) nitrate ? ? • Reactivity of Alkali Metals

Double Replacement • Ions of 2 reactants exchange places in an aqueous solution to form new products • EX: Zinc oxalate + ammonium phosphate → ? ?

More on Double Replacement • Some of the products may exist as ions in an aqueous solution, while others may exist as a solid • Soluble Cmpd (aq) = Exists as ions in solution • Insoluble Cmpd (s) = Exists as a solid in solution

Soluble or Insoluble? ? • Check the solubility chart or rules on reference sheet • Be sure to indicate which product is soluble and which is insoluble!!!!! • Double Replacement - Production of Precipitate

Examples of Solubility • Are these compounds soluble or insoluble? 1. K 2 SO 4 2. Ag. Cl 3. Ba. SO 4 4. Ca. S 5. K 3 PO 4 6. Mg. CO 3

Net Ionic Equations • Includes only the compounds and ions that are chemically changed • Step 1: Write the products in words. Translate into a balanced equation – including states (use solubility rules) • Step 2: Write the overall ionic equation – cancel spectator ions. • Step 3: Write the net ionic equation – including states

Example Zinc nitrate + ammonium sulfide → ? ?

Combustion • A substance reacts with oxygen to produce lots of energy, usually in the form of heat and light

Complete Combustion • C_H_ + O 2 H 2 O + CO 2 + energy • EX: Propane + oxygen gas → ? ? • • • Combustion Video (5 min) Origin of Combustion Engine Part 1(2 min) Origin of Combustion Engine Part 2 (3 min) Hindenburg Disaster (4 min)

Incomplete Combustion C_H_ + O 2 H 2 O + CO 2 + CO + E Dangerous product = CO