Question

study the following phase diagram of substance x. use this diagram to answer the following questions. suppose a small sample of pure x is held at 71. °c and 21.3 atm. what will be the state of the sample? suppose the temperature is held constant at 71. °c but the pressure is decreased by 16 atm. what will happen to the sample? suppose, on the other hand, the pressure is held constant at 21.3 atm but the temperature is decreased by 184. °c. what will happen to the sample?

Explanation:

Step1: Convert temperature to Kelvin

$T = 71^{\circ}C+ 273 = 344K$

Step2: Locate point on phase - diagram

Locate the point with $T = 344K$ and $P=21.3$ atm on the phase - diagram. The point lies in the solid region.

Step3: Calculate new pressure

New pressure $P_{new}=21.3 - 16=5.3$ atm. With $T = 344K$ and $P = 5.3$ atm, the point lies in the gas region. So the sample will sublime (go directly from solid to gas).

Step4: Calculate new temperature

New temperature $T_{new}=71 - 184=- 113^{\circ}C$, $T_{new}=-113 + 273 = 160K$. With $P = 21.3$ atm and $T = 160K$, the point lies in the solid region. Since it was solid initially and remains solid, no phase change occurs.

Answer:

Solid; Sublime; No phase change