Question

Suppose you start with a liquid mixture of 60% nitrogen and 40% oxygen. Describe what happens as the temperature of this mixture increases. Be sure to give the temperatures and compositions at which boiling begins and ends.

Short answer

The vaporising process will continue as the temperature rises.

Step-by-step solution

Given information

Suppose you start with a liquid mixture of 60% nitrogen and 40% oxygen.

Explanation

Temperature diagram for mixture of nitrogen and oxygen

Consider the experimental phase diagram for nitrogen and oxygen at atmospheric pressure in Figure 5.31 of the book. Assume we have a mixture of 40% oxygen and 60% nitrogen, so x=0.4. As the temperature rises, the mixture remains in a liquid state until we reach 80.6 K, at which point the liquid begins to vaporise. If we draw a horizontal line from the lower curve to the upper curve (until they intersect), we can see that x= 0.16 from the upper curve at this temperature, and since pure nitrogen occurs at x = 0, we can conclude the vaporising process will continue as the temperature rises; follow the upper curve until it hits x = 0.40; there can't be any liquid left from oxygen at this point; drawing a horizontal line, we can see that the temperature at this point is 84.5 K.