Help with hexane, bromide ions and Br2.?

Question

By adding some aqueous chlorine to some aqueous bromide ions, chloride ions are formed with bromine solution.

If i then add a solution of hexane to the bromine product what is the colour change for hexane and what does the test show?

Thx

Answer 1

Nothing should happen, since hexane is a fully saturated molecule. If it was hexene that you had then you would notice a coulour change, usually a dirty orange/brown. This would be because the double bond has broken and the bromine has taken its place.

Answer 2

Initially, the chlorine will react with the bromide ions, liberating free bromine:
Cl2 + 2 Br- → Br2 + 2 Cl-
This will impart a pale orange colour to the aqueous solution.
If the reaction mixture is then shaken with hexane, on allowing the whole mixture to settle, the hexane layer will rise to the top and virtually all the orange colour will have been transferred to the hexane layer.

This demonstrates that bromine is more soluble in non-polar solvents (such as hexane) than in polar solvents, such as water.

If the solution of bromine in hexane is exposed to strong sunlight (or ultra-violet light), the orange colour will slowly fade, as the following substitution reaction takes place:
C6H14 + Br2 → C6H13Br + HBr

Answer 3

The idea of adding hexane is to see more clearly the colour of the free halogen at the end. In this experiment it would take most of the orange bromine out of the water, and into the organic hexane layer. The hexane is merely acting as a solvent.

Answer 4

n-Hexane would change from colourless (as the original solvent) to orange. It is a very non-polar solvent that is immiscible with water. With a lower density, it will be the top layer (over the aqueous solution). Since the Br2 produced is quite non-polar, it will be more soluble in the n-hexane layer, giving a more orange colour. This solvent is to to show the orange colour more clearly. There is no chemical reaction involved.

Answer 5

Bromine is much more soluble in hexane and gives an intense brown colour. The hexane is insoluble in water and forms a layer above the water.

Answer 6

The definitive test for alkanes /alkenes is Br2 in H2O (which is what you've made in the first part of the reaction.) It's definitive because in water, Br2 actually exists as HBr and HOBr. HBr is an asymmetric reagent for additon reactions, adding H and Br across a double bond (for alkenes) but it cannot produce the Br free radicals (active species) needed for the monosubstitution reaction undergone by alkanes (such as hexane). So...no colour change.

Answer 7

wow nice question.Bromine has an orange color, Basicaly adding it to an alkane(hexane) there is no color change.This is due to the fairly unreactive nature of alkanes because of the presence of sigma bond.On the other hand alkenes(hexene) turns bromine colourless and in general this test is used to differentiate between alkenes(hexene) and alkanes(haxane).

Answer 8

0.0008M: the M stands for moles per Litre mass=moles /molar mass First find the mass of bromine in one litre of water mass=0.0008/79.91 where the molar mass of bromine is 79.91g/mol mass=1.00113 x 10-05g You want 1 g of bromine thus 1/(1.00113 x 10-05)=99887.5 Litres of water