A student prepared ethene (C₂H₄) gas and bubbled it into a coloured solution in a test-tube to test for unsaturation - Leaving Cert Chemistry - Question 1 - 2017

A positive result is indicated by a color change from brown or red to colorless, confirming the presence of double bonds.

To conduct a combustion test, place a small amount of ethyne gas in a stoppered test-tube and ignite it with a burning taper. Ensure that the test-tube is pointed away from yourself to avoid any hazards.

The flame observed is likely to be sooty and bright yellow due to the incomplete combustion of ethyne, indicating a rich fuel-to-air ratio.

The balanced equation is:

The purpose of the limewater is to confirm the presence of carbon dioxide (CO₂) produced during combustion. If CO₂ is present, limewater will turn cloudy due to the formation of calcium carbonate.

The mobile phase in chromatography is the solvent (usually a liquid) that carries the components through the stationary phase, which is the paper or solid where the components are separated based on affinity.

Three different indicators were separated in the process shown.

The component carried forward is labeled with an F on the chromatography paper.

The indicators were carried at different rates due to varying affinities for the stationary phase and solubilities in the mobile phase. Factors such as polarity and molecular weight contribute to these differences, leading to separation during chromatography.