Fuels - Organic Chemistry

Question 1

Define the terms HYDROCARBON and ORGANIC.

Answer 1

Hydrocarbon - a class of chemical compounds, some of which found in nature (organic), comprising only chains of hydrogen and carbon atoms.

Organic - (of substances) Found in nature.

Question 2

Common properties of all hydrocarbons

Answer 2

• Water insoluble (except alcohols due to oxygen atom addition)
• Increasing chain length increases boiling/melting points
• Combustible
• Soluble in oil-based solvents

Question 3

Which properties are affected by increasing chain length?

Answer 3

• Combustibility (larger alkanes/alkenes are difficult to set alight as well as of low viscosity)
• State at 23˚C ambient temp: 1-4 carbon atoms = gas; 5-17 carbon atoms = liquid; 18 and more carbon atoms = solid

Question 4

Give examples of molecular and condensed structural formula for hexane.

Answer 4

Molecular - C6H14
Condensed structural - CH3 CH2 CH2 CH2 CH2 CH3

Question 5

Properties of alkanes (exclusive)

Answer 5

• All single covalent bonds between adjacent carbon and attached hydrogen atoms
• Saturated compound; very nonreactive with other substances present
• Burn more efficiently than alkenes
• Found in nature as part of crude oil
• General formula = CnH2n+2 (i.e. C4H10, C7H16)

Question 6

Properties of alkenes (exclusive)

Answer 6

• Double covalent bonds between adjacent carbon atoms, but single bonded with hydrogen atoms
• Unsaturated compound; bonds easily with new elements/substances nearby
• Can only be synthesized via cracking a large alkane
• Burn inefficiently and often undergo incomplete combustion
• General formula: CnH2n (i.e C2H4, C9H18)

Question 7

State the suffixes for each type of hydrocarbon.

Answer 7

Alkane: -ane
Alkene: -ene
Alcohol: -anol