Alkenes

Question 1

Features of alkene homologous series?

Answer 1

Contain a C=C double covalent bond (functional group - UNSATURATED)
General formula : CnH2n

Question 2

Key point to note about alkene series

Answer 2

THERE IS NO METHENE (needs C=C double covalent bond)

Question 3

Reactions with alkenes

Answer 3

Can burn in oxygen or air and same products of combustion as alkanes BUT they have C=C double bond functional group - allows them to undergo addition reactions

Question 4

What is a functional group?

Answer 4

An atom, group of atoms, or type of bond in a molecule that is responsible for the characteristic reactions of the substance

Question 5

What are addition reactions

Answer 5

An atom or a group of atoms combine with a molecule to form a larger molecule with no other product

Question 6

Test for unsaturation

Answer 6

Both alkanes and alkenes should be combined with bromine - however only the alkene reacts as it is unsaturated and has a C=C functional group ; it forms dibromoethANE (no double bond). Bromine water is orange brown and it turns colourless when it is mixed with alkenes (BUT NOT WITH ALKANES)

Question 7

Addition reactions with hydrogen

Answer 7

Alkenes undergo addition reactions with hydrogen IN THE PRESENCE OF A NICKEL CATALYST to form an alkane
Ethene + hydrogen -> ethane