Rank the following compounds in order of decreasing boiling point:
sodium fluoride ( \rm NaF ), methane ( \rm CH_4 ), fluoromethane ( \rm CH_3F )
Highest = NaF
Medium = CH3I
Lowest = CH4
Highest- fart
To rank the compounds in the order of decreasing boiling point, we need to consider the strength of intermolecular forces between their molecules. The stronger the intermolecular forces, the higher the boiling point. Here's how we can rank the compounds:
1. Sodium fluoride (NaF): NaF is an ionic compound, meaning it consists of positively charged sodium ions (Na+) and negatively charged fluoride ions (F-). Ionic compounds tend to have high boiling points because of the strong electrostatic attraction between the ions. Therefore, NaF will have the highest boiling point among the given compounds.
2. Fluoromethane (CH3F): Fluoromethane is a polar molecule, as the fluorine atom withdraws electron density from the carbon-hydrogen bond, resulting in a partial positive charge on carbon and a partial negative charge on fluorine. This polarity leads to dipole-dipole interactions between CH3F molecules. These dipole-dipole forces are stronger than the London dispersion forces present in methane (CH4).
3. Methane (CH4): Methane is a nonpolar molecule, and its only intermolecular forces are London dispersion forces, which are weaker than dipole-dipole forces. Since methane only experiences London dispersion forces, it will have the lowest boiling point among the given compounds.
Therefore, the compounds can be ranked in decreasing boiling point as follows:
NaF > CH3F > CH4
To determine the order of boiling points for the given compounds (sodium fluoride, methane, and fluoromethane), we need to consider the intermolecular forces between their molecules. The strength of intermolecular forces affects how tightly the molecules are held together, which in turn affects the boiling point.
1. Sodium Fluoride (NaF):
Sodium fluoride is an ionic compound composed of positively charged sodium ions (Na+) and negatively charged fluoride ions (F-). Ionic compounds have strong electrostatic attractions between ions, called ionic bonds. When NaF is in the solid state, these ionic bonds hold the crystal structure together. However, when heated, the ionic bonds break and the compound melts. Since ionic bonds are very strong, a significant amount of energy is required to break them. Therefore, sodium fluoride has a relatively high melting and boiling point.
2. Methane (CH4):
Methane is a simple hydrocarbon that consists only of carbon atoms bonded to hydrogen atoms. It is an example of a nonpolar molecule. Nonpolar molecules experience weak van der Waals forces, specifically London dispersion forces. London dispersion forces arise due to temporary fluctuations of electron distribution, creating instantaneous dipoles. Although London dispersion forces are weak, they act between all molecules. Methane has a lower boiling point than sodium fluoride due to the weaker intermolecular forces between its nonpolar molecules.
3. Fluoromethane (CH3F):
Fluoromethane is a polar molecule, unlike methane. It consists of a carbon atom bonded to three hydrogen atoms and one fluorine atom. The electronegativity difference between carbon and fluorine causes the molecule to have a partial positive charge on carbon and a partial negative charge on fluorine, creating a dipole. In addition to London dispersion forces, fluoromethane experiences stronger dipole-dipole interactions due to the polarity of the molecule. These dipole-dipole interactions are stronger than the London dispersion forces in methane. As a result, fluoromethane has a higher boiling point than methane.
To summarize, the compounds can be ranked in order of decreasing boiling points as follows:
1. Sodium fluoride (NaF)
2. Fluoromethane (CH3F)
3. Methane (CH4)