Question

ase diagrams
p (atm)
1.5
1.0 w x
0.5 z y
0 -10 0 10 20 30 40 50 60 70
t (°c)
b 1.0 atm and 40 c
c 0.5 atm and 20 c
d 1.4 atm and 50 c
part d
what is the freezing point at stp?
a 40 c
b 5 c
c 15 c
d 50 c
part e
at 1.2 atm and 30 c, the substance is ...
a boiling
b gas
c liquid
d melting
e solid

Explanation:

Part D

STP (Standard Temperature and Pressure) has a pressure of 1.0 atm. To find the freezing point at STP, we look at the phase diagram where pressure \( P = 1.0 \, \text{atm} \). The freezing point is the temperature at the solid - liquid equilibrium line at \( P = 1.0 \, \text{atm} \). From the diagram, at \( P = 1.0 \, \text{atm} \), the temperature corresponding to the freezing point (solid - liquid boundary) is around \( 15^\circ \text{C}\)? Wait, no, let's re - examine. Wait, maybe I made a mistake. Wait, the phase diagram: the point where the solid - liquid and liquid - gas lines meet? Wait, no, STP is 1 atm. Let's check the options. Wait, the correct approach: the freezing point at STP (1 atm) is the temperature at which the substance freezes at 1 atm. Looking at the phase diagram, the solid - liquid equilibrium line at \( P = 1.0 \, \text{atm} \) – wait, maybe the diagram's z point? Wait, no, the options are A 40 C, B 5 C, C 15 C, D 50 C. Wait, maybe I misread. Wait, actually, in a phase diagram, the freezing point at a given pressure is the temperature at the solid - liquid co - existence curve. At STP (1 atm), we look for the temperature on the solid - liquid line at \( P = 1.0 \, \text{atm} \). From the diagram, the x - w - z lines: w is maybe solid, x liquid, y gas? Wait, no, the axes: P (atm) on y, T (°C) on x. The line separating solid and liquid: at P = 1.0 atm, what's T? Wait, the options: C is 15 C? Wait, maybe the correct answer is C? Wait, no, maybe I made a mistake. Wait, let's think again. STP is 1 atm. The freezing point is the temperature at which solid and liquid co - exist at 1 atm. Looking at the phase diagram, the intersection of the solid - liquid line and P = 1 atm. From the graph, at P = 1 atm, the temperature is around 15 °C? So the answer is C.

We have a pressure of \( 1.2 \, \text{atm} \) and temperature \( 30^\circ \text{C} \). In a phase diagram, we need to determine the region. The phase diagram has regions: solid (w), liquid (x), gas (y). At \( P = 1.2 \, \text{atm} \) (which is above 1.0 atm) and \( T = 30^\circ \text{C} \), we check the regions. The liquid region (x) is at higher pressure and moderate temperature compared to gas (y) which is at lower pressure and higher temperature? Wait, no, let's see the axes: P increases upwards, T increases to the right. The line between liquid (x) and gas (y) is the vapor pressure curve. At \( P = 1.2 \, \text{atm} \) (above the vapor pressure at 30 °C, since at 30 °C, the vapor pressure is less than 1.2 atm, as seen from the curve y which is the vapor pressure curve), so the substance is in the liquid phase. So the answer is C (liquid).

Answer:

C. 15 C

Part E