The reactants are cyclopentene and hydrogen.
This reaction is a typical catalitic hydrogenation of an alkene.
The hydrogenation of alkenes in the presence of a catalyst (may be Pd, Pt or Ni) results in the addition of H2 to the double bond. Then the double bond breaks and it is produced an alkane.
In spite of the reaction is thermodinamically favorable to the formation of the alkane a catalyst is needed to overcom the activation energy.
Then the reaction is
Reactants catalyst Product
Cyclopentene + H2 Pd, Pt, or Ni Cyclopentane