Properties of Alkanes Flashcards
What are alkanes?
Alkanes are saturated hydrocarbons containing only carbon and hydrogen atoms joined by single covalent bonds.
What is the general formula for alkanes?
The general formula for alkanes is CnH2n+2.
What is the significance of alkanes in terms of stability?
Alkanes are amongst the most stable organic compounds, which contributes to the longevity of crude oil deposits.
What type of bond is formed between carbon atoms in alkanes?
The bond formed between carbon atoms in alkanes is called a sigma bond.
Fill in the blank: Each carbon atom in an alkane has ______ sigma bonds.
four
What molecular geometry do alkanes exhibit around each carbon atom?
Alkanes exhibit a tetrahedral geometry around each carbon atom.
What is the approximate bond angle in alkanes?
The approximate bond angle in alkanes is 109.5°.
How are different alkanes separated in oil refineries?
Different alkanes are separated in oil refineries by fractional distillation.
What causes the increase in boiling points of alkanes?
The increase in boiling points of alkanes is due to the weak intermolecular forces called London forces.
How does chain length affect the boiling point of alkanes?
As chain length increases, the boiling point increases due to greater surface area leading to stronger London forces.
True or False: Branched isomers of alkanes have higher boiling points than straight-chain isomers.
False
What is the effect of branching on the boiling points of alkanes?
Branched isomers have lower boiling points due to fewer surface points of contact and weaker London forces.
Name the first three alkanes in the homologous series.
- Methane (CH4)
- Ethane (C2H6)
- Propane (C3H8)
What happens to alkanes when intermolecular forces are broken?
When intermolecular forces are broken, the alkane molecules move apart and the substance becomes a gas.
Fill in the blank: A covalent bond is defined as a _______ pair of electrons.
shared
What are London forces?
London forces are weak intermolecular forces that act between molecules in close surface contact.
What happens to the boiling point of alkanes as their molecular mass increases?
The boiling point generally increases as molecular mass increases.
What is the boiling point of pentane (C5H12)?
The boiling point of pentane is 36°C.
Describe the relationship between surface area and London forces in alkanes.
Greater surface area allows for more surface contact, increasing London forces.
What is the effect of the shape of branched alkanes on intermolecular forces?
The shape of branched alkanes prevents them from getting as close together as straight-chain molecules, decreasing intermolecular forces.
