Classifying Equations Chemical Reactions Writing Equations Balancing Equations Classifying Equations Predicting Products

Writing Equations Chemical equations represent changes that occur in a chemical reaction. Reactants – starting substances Always on the left of the arrow Products – substances formed in a reaction Always on the right of the arrow  means “yields” “forms” “produces”

Example: Yields or makes NaCl + AgBr  NaBr + AgCl Reactants Products

State Symbols cr – crystalline solid s - solid g – gas l – liquid aq – aqueous solution

2H2(g) + O2(g)  2H2O(l) Mg (s) + 2HCl (aq)  MgCl2 (aq) + H2 (g)

Writing and Balancing Equations Determine reactants and products. Write correct formulas for each. Add coefficients to balance. the number of atoms of each element must be equal on each side of the equation. Law of Conservation of Matter YOU CANNOT EVER CHANGE SUBSCRIPTS! TO BALANCE EQUATIONS, YOU CAN ONLY ADD COEFFICIENTS!!!!

When zinc reacts with hydrochloric acid, zinc chloride and hydrogen are formed.

When propane burns in oxygen, carbon dioxide and water are formed. C3H8 + O2 CO2 + H2O

Classifying Chemical Reactions Single Displacement One element replaces another in a compound A + BC  AC + B Element + Compounds  Element + Compound + ions replace + ions, – ions replace – ions

Single Replacement 2Ag + ZnCl2  2AgCl + Zn F2 + 2 NaCl  Cl2 + 2 NaF + ion replaces + ion F2 + 2 NaCl  Cl2 + 2 NaF - ion replaces - ion

2. Double Displacement: Two compounds swap ions AB + CD  AD + CB Compound + Compound  Compound + Compound

Double Displacement ZnI2 + CuS  ZnS + CuI2 NaOH + HCl  NaCl + HOH -

Activity Series of Metals Lithium Potassium Calcium Sodium Magnesium Aluminum Zinc Chromium Iron Nickel Lead Hydrogen Bismuth Copper Mercury Silver Platinum Gold *Metals above other metals will replace them in replacement reactions. 2Fe (s) + Pb(SO4)2(aq) + 2Fe(SO4)(aq) + Pb(s) *All metals above H will replace H in acids. 2Al(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2(g) *All metals above Na will replace H in water. Ca(s) + H2O → CaO(aq) + H2(g)

Activity Series for Halogens REMEMBER: Halogens are elements in Group 17 Elements above others will replace them. Cl2(g) + 2NaI(aq) → 2NaCl(aq) + I2(g)

3. Decomposition 1 reactant breaks down to form several products (may be elements or compounds) ABC  A + BC C  E + E or E + C or C + C Example: 2 KClO3  2 KCl + 3 O2

Decomposition Rules: 2MgO  2Mg + O2 Mg(OH)2  MgO + H2O Metallic oxides form metals and oxygen. 2MgO  2Mg + O2 Metallic hydroxides form metallic oxides and water. Mg(OH)2  MgO + H2O Metallic carbonates form metallic oxides and carbon dioxide. MgCO3  MgO + CO2

Metallic chlorates form metallic chlorides and oxygen. Mg(ClO3)2  MgCl2 + 3O2 Oxyacids form nonmetallic oxides and water. H2CO3  CO2 + H2O Compounds decomposed by electrolysis form elements. 2NaCl  2Na + Cl2

4. Synthesis: 2 or more substances combine to form 1 new substance A + B  AB or AB + C  ABC E + E  C or C + E  C Opposite of decomposition meaning more than 1 reactant join to form 1 product

Synthesis N2 + 3 H2  2 NH3 1 product NH3 + HCl  NH4Cl

5. Combustion CnH(2n+2) + O2  CO2 + H2O A hydrocarbon reacts with oxygen to form carbon dioxide and water CnH(2n+2) + O2  CO2 + H2O

Combustion CH4 + O2  CO2 + H2O C8H18 + O2  CO2 + H2O Let’s balance these! CH4 + O2  CO2 + H2O C8H18 + O2  CO2 + H2O

Balance Equations and ID Rxn Type H2S + O2 → H2O + S Cu(NO3)2 + NH4(OH) → Cu(OH)2 + NH4(NO3) NH3 + O2 → N2 + H2O Hg2O + O2 → HgO

Balance Equations and ID Rxn Type C4H10 + O2 → CO2 + H2O H2O → H2 + O2 Ba(NO3)2 + Na2(CrO4) → Ba(CrO4) + Na(NO3)

Predicting Products aluminum plus hydrochloric acid calcium hydroxide plus nitric acid zinc chloride plus hydrogen sulfide

Predicting Products sodium chlorate (heated) barium nitrate plus sodium chromate