Question

Which of the following will decolourise bromine water?

• A. ${\mathrm{C}}_4{\mathrm{H}}_6$
• B. ${\mathrm{C}}_2{\mathrm{H}}_4$
• C. ${\mathrm{C}}_6{\mathrm{H}}_{10}$
• D. None of these

Answer 1

Answer: (A), (B), (C)

${\mathrm{C}}_6{\mathrm{H}}_{10}$

Explanation for the correct option:

Option (a):

• The bromine water test is a confirmatory test for unsaturation.
• The bromine water in carbon tetrachloride is a reddish-brown colour that when added to an unsaturated compound becomes colourless.
• The formula of ${\mathrm{C}}_4{\mathrm{H}}_6$is Butyne.
• The structure of butyne is $\mathrm{HC}\equiv \mathrm{C}-{\mathrm{CH}}_2-{\mathrm{CH}}_3$.
• There is one triple bond and this undergoes this bromine water test.

Option (b):

• The formula of ${\mathrm{C}}_2{\mathrm{H}}_4$is Ethene.
• The structure of butyne is ${\mathrm{H}}_2\mathrm{C}={\mathrm{CH}}_2$.
• There is one double bond and this undergoes this bromine water test.

Option (c):

• The formula of ${\mathrm{C}}_6{\mathrm{H}}_{10}$is Hexyne.
• The structure of butyne is $\mathrm{HC}\equiv \mathrm{C}-{\mathrm{CH}}_2-{\mathrm{CH}}_2-{\mathrm{CH}}_2-{\mathrm{CH}}_3$.
• There is one triple bond and this undergoes this bromine water test.

Explanation for the incorrect option:

Option (d):

• Since options (a), (b) and (c) undergo a bromine water test.
• This option is not applicable.

Final answer:

Hence, options (a), (b), (c) are the correct answer.