Answer any two of the parts (a), (b), (c) and (d) - Leaving Cert Chemistry - Question 11 - 2021

To prepare ethene in the laboratory, one could use the following apparatus setup:

1. Apparatus Description:

   • Use a horizontal test tube placed on a stand.
   • Insert a delivery tube connected to a source of ethene.
   • Use a reagent like ethanol heated in the tube, with a cotton wool plug to control gas flow.
   • Connect the delivery tube to a collection vessel where the ethene gas will be collected.

2. Diagram Features (to be labelled):

   • Heat source under the test tube.
   • Ethanol (indicated in the tube).
   • Collection syringe for ethene gas.
   • Ensure the delivery tube is pointed to the holding syringe.

The product of the reaction between ethene and bromine is 1,2-dibromoethane. The structure can be depicted as:

    Br
    |  
H—C═C—H
    |  
    Br

This shows that the bromine atoms have added across the double bond of ethene.

Ethene is soluble in cyclohexane but insoluble in water due to differences in polarity:

1. Polarity:

   • Cyclohexane is a non-polar solvent. Ethene (C2H4) is also non-polar, facilitating favorable interactions between them, hence its solubility.
   • Water, however, is polar and exhibits hydrogen bonding, leading to an inability of ethene to form strong interactions with water molecules.

2. Interaction Mechanisms:

   • Non-polar molecules like ethene cannot effectively interact with the polar molecular structure of water, resulting in negligible solubility. Thus, this difference in solubility is attributed to the nature of the intermolecular forces at play.