Comparing properties of Alkanes and AlkenesSimilarities:

Properties Alkanes & Alkenes

Solubility in water NoSolubility in organic solvent

Yes

Conductivity NoBoiling and melting point

Low

Molecular formulaEach member of homologous differs from the next/successive member by a unit −CH2−

Molecular mass Each member of homologous differs from the next/successive member of 14 unit

Differences:

Properties Alkanes Alkenes

Reaction with oxygen, O2 gas

It burned with less sooty yellow flame

It burned with a more sooty yellow flame

Reaction with bromine, Br2 water

The reddish-brown colour of bromine water remains unchanged

The reddish-brown colour of bromine water decolourised

Reaction with acidified potassium manganate(VII), KMnO4 solution

The purple colour of acidified potassium manganate(VII)solutions remained unchanged

The purple colour of acidified potassium manganate(VII)solutions was decolourised

1

[SPOT SPM QUESTIONS 2011]ESSAY;

HOW TO IDENTIFY THE ALKANE and ALKENE IN THE BOTTLES?Solutions: i. Substances & Apparatus

ii. Procedure iii. Observations iv. Inference

[10 marks]Sample answerAim: To investigate the liquid in bottle A and B

BA

Test tube A Test tube B

Dropper

Test tube

2

Substances & Apparatus;Bromine water , 2 test tubes, 2 dropper

Procedure;1. The apparatus shown above is prepared.2. 2-5 cm3 bromine water is measured with measuring cylinder 5ml and poured into a test tube. 3. A few drops of liquid from bottle A is put/added with dropper into the test tube, and shake.4. Observations is recorded.5. The experiments is repeated by replace the liquid from bottle A with bottle B.

Observation and inferences:

Test Tube Observation Inference

Liquidin bottle A

The reddish-brown colour of bromine water remains unchanged

Contains alkane

Liquidin bottle B

The reddish-brown colour of bromine water decolorized

Contains alkene

Easylah!

Prepared by;Kamal Ariffin Bin SaaimSMKDBLhttp://kemhawk.webs.com

3