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Flashcards in alkenes Deck (18)
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1

What is present in alkenes?

C=C double bond

2

what is alkenes also known as?

unsaturated hydrocarbons

3

Why is alkenes also known as unsaturated hydrocarbons?

they contain one or more C=C double bonds

4

what is the general formula of alkenes?

CnH2n

5

what are the chemical properties of alkenes?

- combustion
- undergoes addition reaction due to C=C bond -> polymerisation
- b.p of alkene increases as no. of carbon increases

6

what does addition reaction mean?

one molecule combines with another molecule to form a larger molecule with no other products

7

what are the 5 types of addition reaction?

1. addition of halogens (halogenation)
2. addition of hydrogen halide
3. addition of hydrogen (hydrogenation)
4. addition of water (steam) - hydration
5. addition of alkenes (addition polymerisation)

8

what is the equation for halogenation?

ethene + Br2 (orange-red) -> 1,2-dibromoethane (colourless)

9

why is the end product of halogenation colourless?

bromine is removed and added to ethene

10

what is the test halogenation good for?

distinguishing alkenes from alkanes as alkenes will undergo addition reaction while alkanes dont

11

what is the equation for addition of hydrogen halide?

ethene + HBr -> bromoethane

12

what is the equation of hydrogenation?

ethene + H2 -> ethane (occurs through nickel catalyst in the presence of heat)

13

what is the equation for hydration?

ethene + H-OH -> ethanol

14

what is the catalyst for hydration?

H2SO4

15

what does addition of alkenes mean?

many molecules of alkenes join tgt to form giant molecular structure called polymers

16

what does condensation polymerisation mean?

mono mers join tgt to form polymers and lose small molecules as by-product

17

what is the most common by-product?

water

18

what is the equation of condensation polymerisation?

terephthalic acid + ethylene glycerol -> PET + H2O