Question

Use the accompanying phase diagram for carbon to answerthe following questions.

a. How many triple points are in the phase diagram?

b. What phases can coexist at each triple point?

c. What happens if graphite is subjected to very highpressures at room temperature?

d. If we assume that the density increases with anincrease in pressure, which is more dense, graphiteor diamond?

Short answer

The phase diagram of carbon is shown in the above fig. The carbon transforms into different phases at different temperatures and pressure by changing it.

Step-by-step solution

Explaining the triple points of the phase diagram

In the diagram, we have given the points as P and Q.

The points P and Q are the triple points of the phase diagram. The three phases exist at these points at equilibrium.

The triple point phases include

At point A – Graphite, vapor, and liquid

At point B – Diamond, Graphite, and liquid

Explaining the phases that can exist at the triple point

Three phases exist at the triple point is as follows:

Graphite,vapor,andliquidexist in equilibriumat point P.

Diamond, graphite, and liquid exist in equilibrium at point Q.

If graphite is subjected to very high pressures at room temperature 

At very high pressure and lower temperature, the phase will have a higher density than in any phase.

The graphite is under high pressure and, at room temperature, converts its phase into a diamond which is too hard.

So, we can say that pressure isthe function of temperature.

$\mathrm{P}=\mathrm{f}\left(\mathrm{T}\right)$

The denser phase

As the pressure increases and temperature decreases, the density of the phase increases, which causes the phase to become too hard or solid.

In the graph, as pressure increases, the graphite phase density increases, which further changes into the diamond phase.