Its C A is true as someone mentioned before. B is true because it is an alkene. The formula for an alkene is cnH2n which is the case in c7H14 and both alkenes and alkanes are hydrocarbons so D is true leaving C remaining. Also, cycloalkane involves the word alkane (cnH2n+2) which means the formula should have been C7H16 but its c7h14 so it is an alkane so C is false.

Reply 8

confusedchildren

Original post by YasminBedford

a) its emperical and molecular formulae are different
b) it is an alkene
c) it is a cycloalkane
d) it is a hydrocarbon

However it is strange that it doesnt decolourise in bromine water. All alkenes make bromine water go colourless. Maybe there is something wrong with your question?

Reply 9

Guarddyyy

Original post by confusedchildren

However it is strange that it doesnt decolourise in bromine water. All alkenes make bromine water go colourless. Maybe there is something wrong with your question?

Probably a mistype, it certainly does make bromine water colourless.

Reply 10

ChemistryWebsite

Original post by confusedchildren

However it is strange that it doesnt decolourise in bromine water. All alkenes make bromine water go colourless. Maybe there is something wrong with your question?

What is the emperical formula of a cycloalkane? Also C_nH_2n
Hence C could be true.
The fact that the compound doesn't decolourise bromine water is the give away that B is false whilst C would then be true.

Reply 11

YasminBedford

Original post by Guarddyyy

Probably a mistype, it certainly does make bromine water colourless.

I know what you mean - I thought all alkenes turned bromine water colourless?

Reply 12

bozmak

B is the answer. It is false as alkene will always decolourize bromine water which as the question says, this compound doesn't.A: Its empirical formula is CH2 so thats different than molecular one. So this is true.C: This one is a little tricky to understand but when an alkane becomes a cycloalkane then it loses two hydrogen atoms. So this can be C7H16 alkane converted to C7H14 cycloalkane. So this is also true.D: It is definitely a hydrocarbon. I guess this is self-explanatory. True.

Reply 13

Guarddyyy

Maybe you're missing something to the question. C7H14 can either be a cycloalkane (cycloheptane) or an alkene (heptene). If it is a cycloalkane, it will not decolourise bromine water. If it is an alkene, it will decolourise bromine water.

Reply 14

ChemistryWebsite

Original post by TutorsChemistry

They do.
It's not an alkene :smile:

Whenever you see the bromine water test in a question use that to decide whether the substance definitely is or definitely isn't an alkene.

(edited 5 years ago)

Reply 15

thotproduct

Use the fact it doesn't decolourise bromine water to eliminate the option of it being an alkene. So B would be the false statement. Bromine water engages in a reaction mechanism with unsaturated compounds (i.e things with carbon-carbon double bonds, triple, etc), to decolourise the water, and you should know alkenes are unsaturated compounds. The fact that this test provides a negative means that this compound is not an alkene but is a functional group isomer of an alkene, which is an cycloalkane of a sort. These have the same molecular formulae as the alkene form however are alkanes in every other sense, and won't react with bromine water. You know from this statement and what I said earlier that C would be true, and D is true since the compound only contains Carbon and Hydrogen atoms, obviously. So the answer you can both deduct immediately and invalidate the other answers, as B.

Original post by 16AFC

A is false.

are you on crack cuz

Original post by confusedchildren

However it is strange that it doesnt decolourise in bromine water. All alkenes make bromine water go colourless. Maybe there is something wrong with your question?