Alkanes and Alkenes Flashcards
What’s a Hydrocarbon?
A molecular compound that contains ONLY hydrogen and carbon
What’s a saturated hydrocarbon?
- All bonds with other atoms are single bonds
- Alkanes
What are the properties/uses of Alkanes?
- Low reactivity
- Combusts well making them good for fuel
What’s the general formula for Alkanes?
C(n)H(2n+2)
What are the features of Alkenes?
- reactive
- unsaturated (carbon to carbon double bond)
What’s a homologous series?
A series of compounds with the same functional group and similar chemical properties
What are the 4 shortest alkenes?
Ethene (c2h4)
propene
butene
pentene
What’s the structure of alkanes?
- One carbon is bonded to 4 other atoms
What can alkenes be used for?
- Making plastics (polymers)
- Can undergo addition reactions to make new compounds
What’s a functional group?
A functional group is an atom or group of atoms that is mainly responsible for a molecule’s chemical properties
Describe how alkanes and alkenes are oxidised during complete combustion
The alkanes and alkenes react with oxygen. Their carbon atoms and hydrogen atoms gain oxygen.
Why do hydrocarbons make great fuels?
- During combustion reactions when you burn them in oxygen, they give out lots of energy (exothermic)
How does complete combustion occur? - what are the products?
- Hydrocarbons are burnt in plenty of oxygen, all the atoms are fully oxidised, so, the only products are carbon dioxide and water
When does incomplete combustion occur?
- Insufficient reaction means that full oxidation does not occur
- So, carbon monoxide (CO) and carbon in the form of soot can be formed as well
What’s the functional group of alkenes?
C=C
What happens during addition reactions?
ALKENES
C=C bond can open up and allow the two carbons to bond to atoms of another molecule
So, the reactants combine to form one larger product molecule and no other products
What process can alkenes go through to become alkanes?
Addition reactions
What test could you do to determine if something is an alkane or alkene?
Bromine water
Explain the bromine water test
- Bromine water goes from orange-brown to colourless when mixed with alkenes because a chemical reaction occurs
- This works because the C=C double bond reacts with bromine to form a colourless product
- The bromine is therefore removed from the solution, which loses its colour
(alkanes do not have any double bonds so no colour change would occur)
What is formed when an alkene reacts with hydrogen?
Alkane
How many atoms are found in the formula C6H12?
18
What are the dangers of carbon monoxide?
- Toxic gas
- It combines with haemoglobin in red blood cells, preventing oxygen combining
- This reduces the amount of oxygen carried in the bloodstream, so people can become sleepy or unconscious
- Severe carbon monoxide poisoning can cause death
What is the general formula for Alkenes?
CnH2n