Rank the following 3 compounds in terms of increasing boiling point: CCl4, CH4, CH2Cl2

- Rank the following 3 compounds in terms of increasing boiling point: CF4, CH4, CH2F2
- Water, H2O, is a liquid at room temperature. Hydrogen selenide, H2Se, is a homologue compound. At room temperature is it a gas, liquid, or solid?

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To rank compounds based on their boiling points, we need to consider the factors that affect boiling point. The key factor is the strength of intermolecular forces. Generally, compounds with stronger intermolecular forces have higher boiling points.

For the first set of compounds (CCl4, CH4, CH2Cl2), we examine the types of intermolecular forces involved. CCl4 is a nonpolar molecule and exhibits London dispersion forces, which are the weakest intermolecular forces. CH4 is also nonpolar and has similar London dispersion forces. CH2Cl2 is a polar molecule and has dipole-dipole interactions in addition to London dispersion forces.

Since London dispersion forces are the weakest, CCl4 and CH4 will have lower boiling points compared to CH2Cl2. However, between CCl4 and CH4, CH4 has a smaller molecular mass, so its London dispersion forces will be weaker. Thus, the ranking is as follows:

Increasing boiling point: CH4 < CCl4 < CH2Cl2

For second set of compounds (CF4, CH4, CH2F2), we analyze their intermolecular forces. CF4 is a nonpolar molecule and has London dispersion forces. CH4 also has London dispersion forces, and CH2F2 is a polar molecule, so it has dipole-dipole interactions along with London dispersion forces.

Since all three compounds have London dispersion forces, we look at the additional dipole-dipole interactions in CH2F2. Hence, CF4 will have the lowest boiling point, followed by CH4, and then CH2F2:

Increasing boiling point: CF4 < CH4 < CH2F2

For the last question about hydrogen selenide (H2Se), we don't need to consider other compounds. We only need to know whether H2Se is a gas, liquid, or solid at room temperature.

Hydrogen selenide (H2Se) is a volatile compound and possesses low boiling and melting points. Therefore, at room temperature, it exists as a gas.