The reaction between ethyne (C₂H₂) and hydrogen (H₂) is a hydrogenation reaction, specifically an addition reaction where hydrogen atoms add across the triple bond of ethyne, breaking the triple bond to form a C=C first, i.e ethene. Then on further reaction, the C=C reacts with H\(_2\), breaking the C=C to form a C-C bond. i.e ethane (C₂H₆). 

 C\(_2\)H\(_2\) \(^{H_2}_{→}\) X \(^{H_2}_{→}\) Y. 

 C\(_2\)H\(_2\) \(^{H_2}_{→}\) C\(_2\)H\(_4\)  \(^{H_2}_{→}\) C\(_2\)H\(_6\)