From the following organic compounds given below, choose one compound in each case that relates to the description [a] to [d]:
[Ethyne, ethanol, acetic acid, ethene, methane]
(a) An unsaturated hydrocarbon used for welding purposes.
(b) An organic compound whose functional group is carboxyl.
(c) A hydrocarbon which on catalytic hydrogenation gives a saturated hydrocarbon.
(d) An organic compound is used as a thermometric liquid.

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Solution

The compounds given in the question are:
Ethyne, Ethanol, Acetic acid, Ethene, Methane
(a) An unsaturated hydrocarbon used for welding purposes
Ethyne or acetylene( $C_{2} H_{2}$ ) is an unsaturated hydrocarbon that consists of one triple bond which on combustion yields a high amount of energy (about -1300 kJ) that is used for welding purposes.
$\underset{E t h y n e}{2 C_{2} H_{2} (g)} + \underset{O x y g e n}{7 O_{2} (g)} \to \underset{C a r b o n d i o x i d e}{4 C O_{2} (g)} + \underset{W a t e r}{6 H_{2} O (a q)}$
(b) An organic compound whose functional group is carboxyl
Acetic acid whose molecular formula is $C H_{3} C O O H$ , is an organic compound that has a functional group known as the Carboxyl group ( $> C = O$ ).
(c) A hydrocarbon which on catalytic hydrogenation gives a saturated hydrocarbon
Ethene ( $C_{2} H_{4}$ ) is an unsaturated hydrocarbon that undergoes catalytic hydrogenation with the Hydrogen( $H$ ) atom and yields ad saturated hydrocarbon that is Ethane ( $C_{2} H_{6}$ ) as shown below:
$\underset{E t h e n e}{C_{2} H_{4} (g)} + \underset{H y d r o g e n}{2 [H] (g)} \to \underset{E t h a n e}{C_{2} H_{6} (g)}$
(d) An organic compound is used as a thermometric liquid
Ethanol( $C H_{3} C H_{2} O H$ ) is an organic compound that has a lower freezing point due to which it is used as a thermometric liquid.

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