Study the reaction scheme and answer the questions that follow - Leaving Cert Chemistry - Question 9 - 2010

(i) An addition reaction in the scheme is the reaction of C₂H₄ with X (which is likely a halogen addition). (ii) A substitution reaction is the conversion of C₂H₃Cl to C₂H₆, where the chlorine atom is substituted with hydrogen.

The mechanism of reaction Y involves the following steps:

1. Electrophilic attack: The electrophile (such as a proton) interacts with the double bond of ethene, forming a carbocation intermediate.
2. Nucleophilic attack: A nucleophile, such as a chloride ion from HCl, attacks the carbocation to form the final product.
3. Deprotonation: The structure rearranges if necessary, followed by the loss of a proton to regenerate a stable alkane.

(i) Conversion V requires H₂ in the presence of a catalyst such as Pt, Pd, or Ni, and the reaction conditions typically involve heating or using light. (ii) Conversion Z requires Cl₂ in the presence of UV light or heat.

A labelled diagram for conversion X would include an apparatus showing a round-bottom flask with ethylene (C₂H₄) being reacted with appropriate reagents. Labels should indicate components such as the condenser, heating mantle, and any necessary safety equipment.

The two organic intermediates can be illustrated as follows:

1. The first intermediate: C₂H₄ (ethene) reacts to yield C₂H₃Cl (chloroethane).
2. The second intermediate: C₂H₃Cl (chloroethane) can react further with an appropriate reagent yielding C₂H₆ (ethane) in the final step.

Each structure should be clearly labeled with its molecular formula.