Alkanes Flashcards
Where are Alkanes obtained from?
Alkanes are obtained directly from the fractional distillation of crude oil
What does Saturated Hydrocarbons mean?
Saturated= C-C
Hydrocarbons: A compound containing only Hydrogen and Carbon.
What are the properties of Alkanes?
- general formula: CnH2n+2
- carbon-carbon single bond only
- Successive members differ by- CH2 hroup
What is the general formula for Alkanes and how to calculate?
General formula: CnH2n+2
How: n= No.of carbon atoms
remember the prefixes: Must Eat peanut Butter and the suffix for Alkanes
What are the four different Alkanes?
Methane, Ethane, Propane and Butane
follow the chem formula in order to draw the structure
What is the chemical formula and structural formula for Methane?
CH4
description: One C in the middle and 4 hydrogen atoms are linked to the C (carbon) in the middle
What is the chemical formula and structural formula for Ethane?
Chemical formula: C2H6
Description for structural formula: C-C and the three other bonds are taken up by the Hydrogen atoms, looks like a capital H.
What is the Chemical and structural formula for propane?
C3H8
Description: Three carbon atoms that are single bond to each other and the rest of the bonds are taken up by the hydrogen atoms
What is the chemical and structural fornmula for Butane?
C4H10
description: 4 carbon atoms single bond to each other and rest of the bonds are taken up by Hydrogen atoms
What are the two reactions that Alkanes are reactive in?
- Combustion
- Subsitution by Chlorine
What is the word equation for complete combustion of Alkanes?
Methane + oxygen-> Carbon Dioxide+ Water
What is the colour of the flame for complete combustion of Alkanes?
Blue flame
What happens during incomplete Combustion?
Alkanes burn in limited amount of air with a yellow smoky flame
What are the possible products from incomplete combustion of Alkanes?
- carbon (soot)
- Carbon monoxide
- Water
What are the two possible word equations for incomplete combustion of Alkanes?
methane+oxygen= carbon Monoxide (CO) + Water
or
Methane+Oxygen= Carbon + Water
Just remember that Carbon monoxide is produced from the incomplete combustion of a carbon coinating substance
What is the subsitution by Chlorine about?
Each hyrdogen in an Alkane is replaced one at a time by one molecule of Chlorine ti form Chloroalkanes.
What conditions must be met for the Subsitution by Chlorine to take place?
- The reaction must take place in the presence of Sunlight (UV light) as the catalyst
Referring to chlorine subsitution
Describe what happens in the first stage?
One Hydrogen atom from (Methane) is displaced to form (Chloromethane)
What is the chemical equation for the first stage?
CH4 + Cl2->CH3Cl+ HCL
Methane+Chlorine (Diatomic element)= Chloromethane + hydrochloric acid
Describe what happens in the second stage of subsitution?
The second hydrogen is displaced from Chloromethane to form Dichloromethane.
Di means 2
What is the chemical equation for the second stage?
CH3Cl + Cl2-> CH2Cl2 + HCL
Describe the third stage for subsitution
U can also draw it out if want. Remeber to write UV above the arrow.
The third hydrogen is displaced from Dichlormethane to form trichloromethane.
What is the chemical equation for the third stage?
CH2Cl2 + Cl2-> CHCl3 + HCL
Describe what happens in the 4th stage of subsitution?
The fourth Hydrogen is displaced from trichloromethane to form tetrachloromethane.
What is the chemical equation for the 4th stage?
CHCl3 + Cl2-> CCl4 + HCL
What is the overall chemical equation for Chlorine subsitution reaction? Using Methane as an example.
CH4 + 4Cl2-> CCl4 + 4HCL
Explain why Alkanes are not reactive generally?
- Alkanes contain Carbon-Carbon single bonds.
- Each Carbon atoms are already covalently bonded to fo four other atoms.
- Hence, no new atom can be added to each carbon already.
