Question

Iodine, like most substances, exhibits only three phases:

solid, liquid, and vapor. The triple point of iodine is at90 torrand $\mathbf{115}\mathbf{°}\mathbf{C}$. Which of the following statements concerning liquid ${\mathbf{I}}_{\mathbf{2}}$must be true? Explain your answer.

a. ${{\mathbf{I}}_{\mathbf{2}\mathbf{\left(}\mathbf{l}\mathbf{\right)}}}^{}$ is more dense than ${\mathbf{I}}_{\mathbf{2}\mathbf{\left(}\mathbf{g}\mathbf{\right)}}$

b.${\mathbf{I}}_{\mathbf{2}\mathbf{\left(}\mathbf{l}\mathbf{\right)}}$ cannot exist above $\mathbf{115}\mathbf{°}\mathbf{C}$.

c. ${\mathbf{I}}_{\mathbf{2}\mathbf{\left(}\mathbf{l}\mathbf{\right)}}$cannot exist at 1 atmosphere pressure.

d.${\mathbf{I}}_{\mathbf{2}\mathbf{\left(}\mathbf{l}\mathbf{\right)}}$ cannot have a vapor pressure greater than 90torr.

e. ${\mathbf{I}}_{\mathbf{2}\mathbf{\left(}\mathbf{l}\mathbf{\right)}}$ cannot exist at a pressure of 10 torr.

Short answer

The correct answers are (A) and (D).

Step-by-step solution

I2(l) is denser than  I2(g)

The liquid phase existence is impossible below the triple point. The solid-vapor curve is to be determined by the direction of the phase.

Hence, the statement is correct.

Step 2: I2(l)  cannot exist above  115°C

The triple point temperature is $115°C$. It means the equilibrium between three phases of liquid, solid, and vapor.

Hence, the statement is incorrect.

I2(l) cannot exist at 1-atmosphere pressure.

The triple point pressure is 90 torr which is less than the 760 torr. The liquid exists above the triple point.

Hence, the statement is incorrect.

 I2(l) cannot have a vapor pressure greater than 90 torr

We know that the density of the liquid is always more than gases.

Hence, the statement is correct.

 I2(l) cannot exist at a pressure of 10 torr

The triple point pressure is 90 torr. For the liquid phase, the pressure must be greater than 90 torr.

Hence, the statement is incorrect.