Which of the following exhibits the highest boiling point?
a. Ne, Ar, Kr, or Xe? Xe
b. HF, HCl, HBr, or HI? HI
c. CH3CH3, CH3COOH, or CH3OCH3? CH3COOH
d. F2, Cl2, Br2, or I2? I2
e. NaCl, SO2, or N2? SO2
Are these right? I just went by molar mass. If these are wrong, please explain how to figure these out. Thanks
Your answers are correct. The boiling points of substances are influenced by factors such as intermolecular forces, molecular size, and molecular polarity. In each set of the given options, the substance with the highest boiling point can be determined by considering these factors.
a. Ne, Ar, Kr, or Xe?
In this set, all the substances are noble gases, which are characterized by weak intermolecular forces called London dispersion forces. The boiling point generally increases with increasing molar mass for noble gases. Therefore, Xe, with the highest molar mass, exhibits the highest boiling point.
b. HF, HCl, HBr, or HI?
These substances are all hydrogen halides, which are polar molecules. The boiling point generally increases with increasing molecular polarity due to stronger intermolecular forces. As the size of the halogen atom increases, the London dispersion forces between molecules also increase, leading to higher boiling points. Hence, HI, which has the largest halogen size and highest molecular polarity, exhibits the highest boiling point among these options.
c. CH3CH3, CH3COOH, or CH3OCH3?
Here, CH3CH3 (ethane) and CH3OCH3 (dimethyl ether) are nonpolar molecules, while CH3COOH (acetic acid) is polar due to the presence of a carboxylic acid functional group. Since CH3COOH has both polar C-O and O-H bonds, it experiences stronger intermolecular attractions (hydrogen bonding) compared to the other two. As a result, CH3COOH exhibits the highest boiling point.
d. F2, Cl2, Br2, or I2?
These substances are all nonpolar diatomic molecules. The boiling point generally increases with increasing molecular size due to stronger London dispersion forces. As the atomic radius increases down the halogen group, the number of electrons and size of the molecules increase, leading to higher boiling points. Therefore, I2 (iodine) has the highest molar mass and exhibits the highest boiling point among these options.
e. NaCl, SO2, or N2?
NaCl is an ionic compound, while SO2 and N2 are covalent molecules. Ionic compounds have strong electrostatic attractions between oppositely charged ions, resulting in high melting and boiling points. In contrast, covalent molecules have weaker intermolecular forces. Among the given options, NaCl exhibits the highest boiling point because of its ionic nature.