Problem 75 - Chemistry: An Atoms-Focused Approach

Question

The World Anti-Doping Agency (WADA) added xenon and argon to the list of banned substances in \(2014 .\) Which intermolecular forces account for the solubility of Xe and Ar in blood?

Step-by-Step Solution

Answer

Answer: The solubility of xenon (Xe) and argon (Ar) in blood can be accounted for by the London dispersion forces, which are weak intermolecular forces generated by temporary fluctuations in electron distributions around these noble gas atoms. These forces allow the noble gases to interact with and dissolve in blood despite their inert and non-polar nature.

Step 1: Know the Noble Gases

Xenon (Xe) and argon (Ar) belong to the group of noble gases in the periodic table. They are known for their low reactivity due to their complete electron shells, making them stable and chemically inert. Thus, they don't form chemical bonds easily, which means their interactions with other substances, such as blood, must be due to intermolecular forces rather than chemical bonds.

Step 2: Identify the Intermolecular Forces

Intermolecular forces are forces that exist between molecules, influencing properties such as solubility. There are three main types of intermolecular forces: 1. London dispersion forces (LDF): These are weak attractive forces between instantaneous dipoles created by fluctuations in electron distributions around the molecules. 2. Dipole-dipole forces: These forces occur between polar molecules, where positive and negative charges are separated within the molecules, creating distinct poles. 3. Hydrogen bonding: This is a special type of dipole-dipole interaction involving hydrogen (H) bonded to a highly electronegative atom like oxygen (O), nitrogen (N), or fluorine (F).

Step 3: Determine the Applicable Intermolecular Forces for Xe and Ar

Since xenon and argon are noble gases and don't have distinct molecular dipoles or hydrogen bonding interactions, the only applicable intermolecular force is the London dispersion forces. These forces are generated by the temporary fluctuations in electron distribution around the noble gas atoms, creating transient dipoles that attract nearby noble gas atoms or interact with polar molecules.

Step 4: Relate the Intermolecular Forces to Solubility

The solubility of a substance in a solvent typically depends on the relative strengths of the solute-solute, solute-solvent, and solvent-solvent interactions. In the case of xenon and argon dissolving in blood, the solute-solvent interactions are primarily the London dispersion forces between the noble gas atoms and the blood molecules (e.g., water, proteins, etc.). These weak forces allow the noble gas atoms to dissolve in blood by overcoming the attractive forces between blood molecules.

Step 5: Conclusion

The solubility of xenon (Xe) and argon (Ar) in blood can be accounted for by the London dispersion forces, which are weak intermolecular forces generated by temporary fluctuations in electron distributions around these noble gas atoms. These forces allow the noble gases to interact with and dissolve in blood despite their inert and non-polar nature.