Rank the substances in order of increasing boiling point. Ar, Cr, C2H7NO, C3H8O
The boiling point of a substance depends on the strength and type of intermolecular forces present. Generally, the strength of the intermolecular forces increases with increasing molecular weight and polarity.
Ranking the substances in order of increasing boiling point:
1. Ar (Argon) – Ar is a noble gas and exists as individual atoms with weak London dispersion forces between them. It has the lowest boiling point among the given substances.
2. C3H8O (Propanol) – Propanol is an alcohol that exhibits stronger intermolecular forces compared to Ar due to the presence of hydrogen bonding. Hydrogen bonding increases the boiling point, making it higher than that of Ar.
3. Cr (Chromium) – Cr is a solid metal with metallic bonding, which involves strong forces of attraction between metal cations and delocalized electrons. Since it is a solid at room temperature, its boiling point is significantly higher than that of propanol.
4. C2H7NO (DMF – Dimethylformamide) – DMF is a polar solvent with a higher molecular weight compared to propanol. It exhibits dipole-dipole interactions and hydrogen bonding, making its intermolecular forces stronger and, hence, having the highest boiling point among the given substances.