Answer to Question #327980 in General Chemistry for Tesha

Question

Phase Diagram for Methane

1. What are the approximate temperature and pressure at the critical

point?

2. What are the approximate temperature and pressure at the triple

point?

3. Is methane a solid, liquid, or gas at 1 atm and 0 ºC?

4. What phase(s) will exist at point 1?

5. If solid methane at 1 atm is heated while the pressure is held

constant, will it melt or sublime?

Answer 1

1. P = 45.99 bar

t = - 82.6 °C

2. P = 0.117 bar

t = - 182.5 °C

3. The intersection of 0 °C and 1 atm is marked point 2 it is in the gaseous region

4. The three phases (gas, liquid and solid)

5. Starting at P = 1 atm and moving horizontally, liquid region is reached at T -180 °C then into the gaseous region, at T ~ - 160 °C. So, solid methane melts in order for methane to sublime, the pressure must be below the triple point pressure.