11SCIE Chemistry 2

Hydrocarbon

Compound made up of only hydrogen and carbon.

CH4

methane

C2H6

Ethane

C3H8

Propane

C4H10

butane

C5H12

Pentane

C6H14

hexane

C7H16

heptane

C8H18

octane

Alcohol general formula

CnH2n+1OH

alkane general formula

CnH2n+2

Methanol

CH3OH

Ethanol

C2H5OH

Complete combustion

all C-C and C-H bonds are broken, meaning all the C and H atoms have reacted with O atoms to form CO2 and H2O molecules

Incomplete combustion

Fuel burns with limited oxygen, so carbon is only partly oxidized, producing CO, C (soot), and H2O instead of CO2

conditions for complete combustion

needs sufficient oxygen

conditions for incomplete combustion

• limited oxygen

• very limited oxygen

observations of complete combustion

• CO2 and H2O molecules are formed

• flame colour is blue

• more energy released than incomplete combustion

observations of incomplete combustion

• limited oxygen = H2O + CO formed

• very limited oxygen = H2O + C formed

• flame is yellow because of the soot glowing

• less energy released than complete combustion

• carbon atoms that are not reacted appear as soot

incomplete combustion word equations

• hydrocarbon + limited oxygen - > carbon monoxide + water

• hydrocarbon + very limited oxygen - > carbon + water

complete combustion word equations

hydrocarbon + oxygen - > carbon dioxide + water

Carbon dioxide and the greenhouse effect

• human activity such as combustion of fossil fuels and transportation increases CO2 concentration in the atmosphere

• increase in CO2 concentration increases the amount of infrared trapped in the atmosphere, warming up the Earth

greenhouse gases

• CO2. weaker but stays in the atmosphere for longer

• CH4 and H2O. stronger but stays for shorter

Combination reaction

when two elements join to form a compound (A + B - > AB)

Displacement reaction

• when a single element (usually a metal) replaces another element in a compound ( A + BC - > AC + B)

• a more reactive metal displaces a less reactive metal

Exchange (Precipitation) reaction

A reaction where two soluble ionic compounds in solution exchange ions, forming a new insoluble compound (a precipitate) that separates out of the solution

Spectator ions

ions that do not change in the chemical reaction