phase diagram
3.0
2.0
pressure / atm
1.0
0.0
0 25 75 125
temperature / °c
part a
what is the temperature of the critical point?
a 75 c
b 15 c
c 100 c
d 2 c
part b
what is the boiling point at stp?
a 60 c
b 25 c
c 100 c
d 80 c
part c
what is the pressure of the triple point?
a 55 atm
b 2 atm

Question

Accepted Answer

### Part A
# Brief Explanations:
To find the critical point's temperature, we analyze the phase diagram. The critical point is the end of the liquid - gas equilibrium curve. From the diagram, the critical point's temperature (looking at the x - axis which is temperature in °C) is around 100 °C (option C). The other options (75 °C, 15 °C, 2 °C) do not match the position of the critical point on the phase diagram.
# Answer:
C. 100 C

### Part B
# Brief Explanations:
STP (Standard Temperature and Pressure) has a pressure of 1 atm. We look at the liquid - gas equilibrium curve (the curve where phase change between liquid and gas occurs) at a pressure of 1 atm. From the phase diagram, the temperature at which the pressure is 1 atm on this curve is around 80 °C? Wait, no, wait. Wait, the x - axis is temperature. Wait, the curve for liquid - gas: at 1 atm (y - axis = 1.0 atm), the temperature on the curve. Wait, looking at the diagram, the point on the liquid - gas curve at 1 atm: the x - axis (temperature) at that point. Wait, maybe I made a mistake. Wait, the options: A is 60, B is 25, C is 100, D is 80. Wait, the liquid - gas curve: the boiling point at STP (1 atm) is the temperature where the vapor pressure equals 1 atm. From the phase diagram, the point on the liquid - gas curve at 1 atm (y = 1.0) has x (temperature) around 80? Wait, no, maybe the correct answer is D? Wait, no, let's re - check. Wait, the phase diagram: the x - axis is temperature from 0 to 125, y - axis pressure from 0 to 3. The liquid - gas curve (the curved line) has a point at 1 atm (y = 1) and x around 80? Wait, the options: D is 80 C. So the boiling point at STP (1 atm) is 80 C (option D).
# Answer:
D. 80 C

### Part C (Note: The options are not fully visible, but assuming the triple point is where all three phases coexist, the pressure at triple point is the pressure at the intersection of the three phase boundaries. From the diagram, the triple point is at a pressure less than 1 atm, but if one of the options is around 0.5 atm or similar, but since the visible options start with A: 55 atm (too high), B: 2 atm (maybe? Wait, no, the triple point pressure is low. Wait, maybe there is a typo, but assuming the correct option (if we consider the diagram, the triple point is at a pressure around 0.5 atm, but if the options have a low pressure, but since the given options for part C are not fully shown, but if we assume the intended answer, maybe a low pressure. But since the user's image for part C has A: 55 atm, B: 2 atm (maybe), but perhaps the correct answer is a low pressure, but due to incomplete options, but if we proceed with the visible part, but maybe the user made a typo. However, based on typical phase diagrams, the triple point pressure is low, much less than 1 atm. But since the options given (A:55 atm is too high, B:2 atm is high, maybe the intended answer is a low pressure, but since the options are not fully shown, we can't be sure. But if we assume the options are like A:55 atm, B:2 atm, C:0.5 atm, D:1 atm, then the triple point pressure is low, so maybe C or D, but without full options, it's hard. But perhaps the user intended to show more, but based on the given, we can't answer fully. But for the sake of the problem, if we assume the triple point pressure is around 0.5 atm (not in the given visible options), but maybe there is a mistake. However, if we proceed with the visible options, and assume that the correct option is a low pressure, but since the options are not fully shown, we can't provide a definite answer. But if we consider the initial problem, maybe the triple point pressure is around 0.5 atm, but since the options are not complete, we will stop here for part C as the options are incomplete.

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QUESTION IMAGE

Question

Explanation:

Part A

Answer:

Part B