Combustion

Hydrocarbons Ethyne (acetylene) C2H2 Methane CH4 Butane C4H10

Complete Combustion Occurs when there is plentiful O2 gas Produces ONLY CO2 (g) and H2O(g) Note: not liquid water CxHy + O2 (g)  CO2 (g) + H2O(g) Lots of oxygen, fuel-lean

Complete combustion of ethyne C2H2 (g) + O2 (g) 

Complete combustion of ethyne C2H2 (g) + O2 (g)  CO2 (g) + H2O(g) Balancing tip: C, then O, then H

Complete combustion of ethyne 2 C2H2 (g) + 5 O2 (g)  4 CO2 (g) + 2 H2O(g) Balancing tip: C, then O, then H

What if oxygen is limited? C2H2 (g) + 3 O2 (g) 

What if oxygen is limited? C2H2 (g) + 3 O2 (g)  CO2 (g) + H2O(g)

What if oxygen is limited What if oxygen is limited? C2H2 (g) + 3 O2 (g)  CO2 (g) + H2O(g) Can’t balance!

Incomplete Combustion Occurs when there is not enough O2 gas Produces C(s) CO(g) CO2 (g) and H2O(g) CxHy + O2 (g)  C(s) + CO(g) + CO2 (g) + H2O(g) Not enough oxygen, fuel-rich

Properties of products H2O(g) C and IC combustion Cobalt chloride paper turns from blue to pink CO2 (g) Limewater cloudy

Properties of products C(s) IC combustion only Solid carbon-rich molecules (“soot”) Inhalation hazard CO(g) C and IC combustion only Toxic gas – silent killer

Combustion Complete Incomplete Blue flame No residue Hotter Uses all energy available Yellow flame Sooty residue Colder Wastes energy Toxic gas produced Inhalation hazard Lights faster

Review

Quiz Zinc is added to a solution of copper nitrate. Barium nitrate and potassium carbonate are mixed. When current passes through water, two gases are formed. Sulfuric acid, H2SO4 (aq) is dropped onto steel wool.

Potassium sulfate and iron (III) chloride are mixed Potassium sulfate and iron (III) chloride are mixed. Sodium metal is placed in a flask containing fluorine gas. Nickel (II) sulfite in aqueous solution is mixed with hydrofluoric acid.

Quiz Copper is added to a solution of zinc nitrate. Cu(s) + Zn(NO3)2(aq)  NR NR Barium iodide and potassium carbonate are mixed. BaI2(aq) + K2CO3(aq)  BaCO3(s) + 2 KI(aq) DD When current passes through water, two gases are formed. 2 H2O(l)  O2(g) + 2 H2(g) D Sulfuric acid, H2SO4 (aq) is dropped onto steel wool. Fe(s) + H2SO4(aq)  FeSO4(aq) + H2(g) SD

Potassium sulfate and iron (III) chloride are mixed Potassium sulfate and iron (III) chloride are mixed. K2SO4(aq) + FeCl3(aq)  NR NR Sodium metal is placed in a flask containing fluorine gas. 2 Na(s) + F2(g)  2 NaF(s) S Nickel (II) sulfite in aqueous solution is mixed with hydrofluoric acid. NiSO3(aq) + 2 HF (aq)  NiF2(aq) + H2O (l) + SO2 (g) DD, D

Chapter Review Chapter 4 Review #39-80 except 47,53 Pick and choose Chapter 5 Review #35-39, 43, 54, 57, 59, 63, 76

Homework Unit summary sheet for test Be prepared for Monday Read 5.1