14.4 Alkane

Question 1

What is alkane

Answer 1

Formula: CnH(2n+2)

They are hydrocarbons which only have single covalent bonds in their structure - they are saturated

Question 2

What is saturated

Answer 2

no more atoms can be added to their molecules

Question 3

Physical properties of alkane

Answer 3

Colorless
First 4 members are gases at rtp, 5-17 are liquid and >17 are solid
Carbon chain gets longer -> BP increase
The difference in BP from 1 alkane to the next also gets smaller as the number of C atoms increase

Question 4

Chemical properties of alkane

Answer 4

Unreacitve - do not react with acids or alkalis

burn with a clean blue flame if there is plenty of oxygen or air present

Question 5

combustion of alkane

Answer 5

Complete combustion - CO2 and H2O form

Not enough oxygen -> incomplete combustion -> CO/C and H2O are formed

Question 6

Reaction of alkane and chlorine

Answer 6

Alkane need light to react with chlorine
If they react, the green color of Cl disappear
It is photochemical reaction and substituition reaction - a chlorine atom replaces a hydrogen atom in the alkane
If we use excess chlorine, we can substitute more H atoms
Similar reaction can happen with other alkane and halogens

Question 7

Equation for reaction between Chlorine and alkane

Answer 7

CH4(g) + Cl2 (g) –light–> CH3Cl (g) + HCl (g) - chloromethane
CH3Cl + Cl2 -> CH2Cl2 + HCl - dichloromethane