Chapter 21, Problem 11STP

Interpretation Introduction

Interpretation:

The temperature and pressure should be determined when the substance is at its triple point.

Concept introduction:

When energy or heat is gain or lost by any matter, the matter changes its state to form a state of matter.

State of matter is classified as:

1. Solid
2. Liquid
3. Gas

A graphical diagram which represents the physical states of a substance under different values of temperature and pressure is known as phase diagram.

The general representation of phase diagram is:

Triple point of a substance is defined as the point at which solid, liquid and gas phase or state of that substance coexist in the equilibrium.

Answer to Problem 11STP

The value of temperature and pressure of a substance at triple point is 13

$-70°\text{C}$ and 5 atm.

Explanation of Solution

The three curves of solid, liquid and gas phase when intersects at a point is known as triple point.

The given graph is:

A line should be drawn parallel to y- axis from triple point towards x-axis. Now, the point at which line intercept the x-axis gives the value of temperature with respect to triple point.

Graph can be redrawn as:

Therefore,

On x-axis, value of pressure is 5 atm.

On y-axis, value of temperature is $-70°\text{C}$.

Hence, the value of temperature and pressure of a substance at triple point is $-70°\text{C}$ and 5 atm.