Module 4: Chapter 12 - Alkanes Flashcards
What is a homologous series?
A group of molecules that have:
1. same functional group
2. same general formula
3. each successive molecule differs by CH2 as you go down the group
What type of hydrocarbons are alkanes? What does this mean?
Saturated hydrocarbons. Contain a C-C single bonds.
What is the general formula for alkanes?
C(n)H(2n+2)
When carbon orbitals overlap, what do they form?
sigma bonds which can rotate freely.
What is the shape around each carbon? What is the bond angle?
Tetrahedral - 109.5 degrees.
Why does boiling point increase as the alkake size increases?
- As molecules get bigger, more electrons are present.
- London forces become strou]nger as there are more electrons.
- More energy required to break them.
- Increasing boiling point.
Why do branched molecules have lower boiling points?
- Branching reduces surface contact.
- Fewer London Forces
- Less energy needed to break them.
- Lower boiling point.
Why are alkanes quite unreactive?
- C-C and C-H bonds are strong = sigma bonds
- C-C bonds are non polar.
- C-H bonds are effectively non polar.
What does a Complete combustion reaction form?
CO2 + H2O
What does an Incomplete combustion reaction form?
Carbon Monoxide, Carbon and Water
Why is CO bad?
It is colourless, odourless and tasteless.
Why is C bad?
In the form of soot, which causes respiratory problems.
What is the equation for complete combustion?
C(x)H(y) + (x+y/4)O2 –> (x)CO2 + (y/2)H2O
What does UV light cause?
UV lights causes the bond between the halogens to undergo homolytic fission.
What are free radicals?
Free Radicals are atoms or molecules with an odd number of electrons, and are very reactive.
