The phase diagram of a substance is shown below.
-The approximate normal melting point of this substance is
A)100 K.
B)190 K.
C)300 K.
D)430 K.

Question

The phase diagram of a substance is shown below. 
-The approximate normal melting point of this substance is
A)100 K. 
B)190 K. 
C)300 K. 
D)430 K.

Quizplus · Accepted Answer

The normal melting point of a substance is the temperature at which it melts at a pressure of 1 atmosphere. Looking at the phase diagram, we can see that the solid-liquid equilibrium line intersects with the pressure axis at around 1 atm and the temperature axis at around 190 K. Therefore, the approximate normal melting point of this substance is 190 K, which corresponds to choice B.

The Phase Diagram of a Substance Is Shown Below