Question

out of the compounds below, which is most likely to be a gas at room temperature (only one is a gas). ethanol ch3ch2oh perfluoropentane c5f12 perchloroethane c2cl6 perfluoroethane c2f6 acetic acid ch3cooh

Explanation:

Step1: Consider intermolecular forces

Compounds with weaker intermolecular forces are more likely to be gases at room - temperature. Hydrogen bonding, dipole - dipole forces, and London dispersion forces affect the state of a compound. Ethanol ($CH_3CH_2OH$) and acetic acid ($CH_3COOH$) have hydrogen bonding due to the $-OH$ group, which leads to stronger intermolecular forces and higher boiling points, making them liquids at room temperature.

Step2: Analyze molecular size and mass for non - polar compounds

Perchloroethane ($C_2Cl_6$) and perfluoropentane ($C_5F_{12}$) are non - polar compounds. Larger and heavier molecules have stronger London dispersion forces. $C_2Cl_6$ has a relatively large molecular mass due to the heavy chlorine atoms, and $C_5F_{12}$ also has a significant molecular mass due to the number of fluorine atoms. These stronger London dispersion forces keep them as liquids or solids at room temperature.

Step3: Evaluate perfluoroethane

Perfluoroethane ($C_2F_6$) is a small non - polar molecule. It has relatively weak London dispersion forces compared to the other non - polar compounds with larger molecular masses. Its low molecular mass and small size result in weaker intermolecular forces, making it a gas at room temperature.

Answer:

Perfluoroethane $C_2F_6$