Final answer:
The correct order based on increasing boiling points for CBr4, Br2, Cl2, and CH4 is CH4, Cl2, Br2, and CBr4. This is because as the molecular size and molar mass increase, so do the London dispersion forces, resulting in a higher boiling point. Therefore, the correct order is option A.
Step-by-step explanation:
To rank these molecules in order of increasing boiling point from lowest to highest, we need to consider their molecular sizes and the types of intermolecular forces present. The main intermolecular force in these nonpolar molecules is the London dispersion forces, which increase with the size and molar mass of the molecules. Given the four options and the molecules CBr4, Br2, Cl2, and CH4, the correct order starting with the lowest boiling point to the highest is:
CH4 < Cl2 < Br2 < CBr4
Methane (CH4) has the lowest boiling point due to its small size and low molar mass. Chlorine (Cl2) is larger than methane and thus has a higher boiling point. Bromine (Br2) is even larger with a higher molar mass than chlorine, leading to a higher boiling point. Finally, carbon tetrabromide (CBr4) has the largest molar mass and size among the four, which results in the highest boiling point.