chem prac (1 Viewer)

[shkspeare]

identify data, plan and perform a first-hand investigation to compare the reactivities of appropriate alkenes with the corresponding alkanes in bromine water

mmmm ok the only thing here i need help with is the equation

i left my books at some1z house so yea :S

i need help with the equation im not sure if its rite

for cyclohexane + bromine water

C6H12 (?) + Br2(aq) ---> C6H11Br(?) + HBr(?)

cyclohexene + bromine water

C6H10 (?) + Br2(aq) ---> C6H10Br2(?)

ok im not really sure of the states either 0.o ne1 help plz??

 

[abdooooo!!!]

ahh... haven't done chem in a long time... but i think it is...

for cyclohexane + bromine water:

CH3-CH2-CH2-CH2-CH2-CH3(l) + HOBr(aq) ---> u.v. a long time ----> CH3-CH2-CH2-CH2-CH2-CH2Br(l) + H2O(l)

for cyclohexene + bromine water:

CH3-CH2-CH2-CH2-CH=CH2(l) + HOBr(aq) ---> CH3-CH2-CH2-CH2-CHOH-CH2Br(l)

 

[Xayma]

Actually cyclohexane is C6H12, it loops back on itself, getting rid of 2 hydrogens to form the last carbon-carbon bond.

 

[shkspeare]

how do u tell if something is aqueous again

something about water.. i forgot... argh

 

[abdooooo!!!]

Originally posted by Xayma
Actually cyclohexane is C6H12, it loops back on itself, getting rid of 2 hydrogens to form the last carbon-carbon bond.

oops... my mistake... thought it was hexane

 

[abdooooo!!!]

Originally posted by shkspeare
how do u tell if something is aqueous again

something about water.. i forgot... argh

water? aqueous is water... that means something dissolved in water.

 

[shkspeare]

so basically something that is polar is aqueous ?

 

[abdooooo!!!]

in water that is... yes.

edit: it also could be ionic... it could be umm... crap im forgetting stuff.

 

[shkspeare]

mm also i thought bromine water was Br2...

 

[abdooooo!!!]

well you could write it as Br2 dissolved in water... but it kinda turns into HOBr... thus the name bromine water.

 

[shkspeare]

thx ab

 

[abdooooo!!!]

no problems

hey i've some notes on that dot point here it is if you need it:

1.3.2 Identify, plan and perform a first-hand investigation to compare the reactivities of alkenes with the corresponding alkanes in bromine water.

Procedure:
1mL of (Bromine water), a clear orange-brown liquid
Added to 1mL solutions of (cyclohexane) and (cyclohexene) in different test tubes, both clear colourless liquids

Result:
Cyclohexene decolourises the bromine water
Cyclohexane only decolourises the solution after long period of exposure to u.v, light

Conclusion:
CH3CH2CH2CH2CH=CH2 + HOBr → CH3CH2CH2CH2CHOHCH2Br
Alkene is more reactive than Alkane because of its double bond
Alkene undergoes addition reaction
Alkane undergoes substitution reaction in the presence of u.v. radiation

Justification:
(cyclohexane) and (cyclohexene) were selected because they are both liquid at room temperature
and only varied by a double bond keeping all other variables constant
(Bromine water) was selected because its a liquid and it has a distinct colour
liquid were necessary in order to observe colour change

Safety and risk:
all chemicals used are harmful if ingested or inhaled (and through skin contact)
(cyclohexane) and (cyclohexene) are highly flammable

Safe work practice:
safety glasses, gloves
effective ventilation (opening windows) or work in fume cabinet
remove all sources of ignition from the working area
Work near readily supplies of water to put out fire
only small amounts (1mL) of each substance is used to minimise waste, pollution, and for safety

 

[shkspeare]

wow thx a lot!

 

[shkspeare]

ok so if i used bromine water as br2

wud it be

Cyclohexane and Bromine Water
C6H12 (l) + Br2 (aq) --> C6H11Br (l) + HBr(aq)

Cyclohexene and Bromine Water
C6H10 (l) + Br2 (aq) --> C6H10Br2 (aq)

 

[abdooooo!!!]

i have no idea... im not your teacher nor am i a hsc marker... i've suffered many injustices under the hands of hard marking teachers.

i recommend you go for HOBr instead...

anyways here is a pic of what i would write in the exam or whatever

 

[shkspeare]

oooo icic

mmm yea.. mayb i shud ask a teacher for using Br2

thx