Question

1. which of the following best helps to explain why hexane has a higher boiling point than methanol has?

(a) methanol molecules can form hydrogen bonds with other methanol molecules.
(b) hexane cannot form hydrogen bonds with other hexane molecules.
(c) methanol molecules have attractions to one another due to london dispersion forces.
(d) hexane molecules have electron clouds that are larger than those of methanol molecules.

1. a 50 ml sample of ( c_{6}h_{14}(l) ) is mixed with a 50 ml sample of ( h_{2}o(l) ), and the mixture is shaken vigorously. the two liquids do not stay mixed but instead form two separate layers. the density of hexane is 0.66 g/ml, and the density of water is 1.00 g/ml. a 1.0 g sample of ( i_{2}(s) ) is added to the mixture, which is shaken again. which of the following best predicts what happens to the ( i_{2}(s) )?

(a) ( i_{2} ) will be found mainly in the top layer because it will dissolve more in the ( h_{2}o(l) ).
(b) ( i_{2} ) will be found mainly in the bottom layer because it will dissolve more in the ( h_{2}o(l) ).
(c) ( i_{2} ) will be found mainly in the top layer because it will dissolve more in the ( c_{6}h_{14}(l) ).
(d) ( i_{2} ) will be found mainly in the bottom layer because it will dissolve more in the ( c_{6}h_{14}(l) ).

1. at 298 k and 1 atm, ( br_{2} ) is a liquid with a high vapor pressure, and ( cl_{2} ) is a gas. those observations provide evidence that under the given conditions, the

(a) forces among ( br_{2} ) molecules are stronger than those among ( cl_{2} ) molecules
(b) forces among ( cl_{2} ) molecules are stronger than the ( cl - cl ) bond
(c) ( br - br ) bond is stronger than the ( cl - cl ) bond
(d) ( cl - cl ) bond is stronger than the ( br - br ) bond

Explanation:

11.

• Density comparison: Hexane (\(C_{6}H_{14}\)) has a density of \(0.66\ g/mL\) and water (\(H_{2}O\)) has a density of \(1.00\ g/mL\). So, hexane will form the top - layer and water will form the bottom - layer.
• Solubility principle ("like dissolves like"): \(I_{2}\) is a non - polar molecule. Hexane (\(C_{6}H_{14}\)) is a non - polar hydrocarbon. Water (\(H_{2}O\)) is a polar molecule. Non - polar \(I_{2}\) will dissolve more in non - polar hexane.

• Intermolecular forces and physical state: The physical state of a substance (gas, liquid, solid) at a given temperature and pressure is related to the strength of intermolecular forces.
• Vapor pressure and intermolecular forces: A higher vapor pressure for \(Br_{2}\) (liquid) compared to \(Cl_{2}\) (gas) at the same temperature (\(298\ K\)) and pressure (\(1\ atm\)) implies that it is easier to convert \(Br_{2}\) molecules from the liquid phase to the gas phase than \(Cl_{2}\) molecules. But actually, \(Br_{2}\) is a liquid and \(Cl_{2}\) is a gas. Stronger intermolecular forces hold \(Br_{2}\) molecules together more tightly in the liquid phase. The bond strength (\(Br - Br\) or \(Cl - Cl\)) is related to intramolecular forces (forces within a molecule), not the physical state which is related to intermolecular forces (forces between molecules).

Answer:

D. \(I_{2}\) will be found mainly in the top layer because it will dissolve more in the \(C_{6}H_{14}(l)\)

12.