Chapter 10: Problem 36

Iodine, like most substances, exhibits only three phases: solid, liquid, and vapor. The triple point of iodine is at 90 torr and \(115^{\circ} \mathrm{C}\) . Which of the following statements concerning liquid \(\mathrm{I}_{2}\) must be true? Explain your answer. a. \(\mathrm{I}_{2}(l)\) is more dense than \(\mathrm{I}_{2}(g) .\) b. \(\mathrm{I}_{2}(l)\) cannot exist above \(115^{\circ} \mathrm{C}\) c. \(\mathrm{I}_{2}(l)\) cannot exist at 1 atmosphere pressure. d. \(\mathrm{I}_{2}(l)\) cannot have a vapor pressure greater than 90 torr. e. \(\mathrm{I}_{2}(l)\) cannot exist at a pressure of 10 torr.

Short Answer

Expert verified

The correct answer is: Liquid I2 cannot exist at 1 atmosphere pressure (statement c) and liquid I2 cannot exist at a pressure of 10 torr (statement e). This is because the triple point pressure for iodine is 90 torr, and at pressures below this value, iodine can only exist as a solid or gaseous phase, not as a liquid phase.

Step by step solution

Statement a: Density comparison of I2(l) and I2(g)

Liquid I2 is more dense than gaseous I2 because molecules in a liquid are closer together than in a gas. This is a general property of matter in different phases, not specific to iodine or its triple point conditions.

Statement b: Existence of I2(l) above 115°C

I2(l) can exist above 115°C if the pressure conditions are altered. The triple point only signifies that at 90 torr and 115°C, all three phases can coexist. Changing the temperature and pressure can still allow liquid iodine to exist.

Statement c: Existence of I2(l) at 1 atmosphere pressure

I2(l) cannot exist at 1 atmosphere (atm) pressure because the triple point pressure is lower (90 torr). One atmosphere is approximately 760 torr, which means that at 1 atm pressure, iodine will only exist as a solid or gaseous phase, not as a liquid phase.

Statement d: Vapor pressure of I2(l) greater than 90 torr

The vapor pressure of I2(l) can be greater than 90 torr if the temperature is increased above the triple point temperature (115°C). Vapor pressure is directly related to temperature. So, as the temperature increases, so does the vapor pressure of a liquid phase.

Statement e: Existence of I2(l) at a pressure of 10 torr

I2(l) cannot exist at a pressure of 10 torr because the triple point pressure is 90 torr. Since 10 torr is below the triple point pressure, at this pressure, the substance can only exist as a solid or gaseous phase, not as a liquid phase. In conclusion, among the given statements, statements c and e must be true for liquid iodine.

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Short Answer

Step by step solution

Statement a: Density comparison of I2(l) and I2(g)

Statement b: Existence of I2(l) above 115°C

Statement c: Existence of I2(l) at 1 atmosphere pressure

Statement d: Vapor pressure of I2(l) greater than 90 torr

Statement e: Existence of I2(l) at a pressure of 10 torr

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