A phase diagram is a graph that illustrates under what conditions the states of

Question

A phase diagram is a graph that illustrates under what conditions the states of matter exist. For example, in the phase diagram of water above, it should be noted that at 1 atm of pressure and 50 degree C, H_2O exists as a liquid. The dark solid lines represent the boundaries between different states. The term "vapor" is used instead of "gas" because vapor describes a substance that is normally a liquid at STP. The line that divides the liquid area from the vapor area has a special name: the vapor pressure curve. To the left of the line, liquid exists. To the right of the line, vapor (gaseous HjO) exists. Right on the line, for example when the pressure is 1 atm and the temperature is 100 degree C, both liquid and vapor exist at the same time. When two or more things coexist at the same time it is called "equilibrium". During equilibrium, liquid changes to vapor and vapor changes to liquid all at the same time and rate. a. How does lowering the pressure affect the boiling point? b. Estimate the boiling point of water when the pressure on the water is 0.1 atm.___ c. From the phase diagram, estimate the vapor pressure of water at 25 degree C.___ d. What is the vapor pressure of water when the temperature is 100 degree C?___

Explanation / Answer

With lowering of the vapor pressure, the boiling point of the water gets decreases .This effect is clearly seen in the phase diagram.

(b) draw a straight line horizontally on the liquid- vapor curve from y-axis.now draw vertical line from that intersection point to the x-axis .

From the given graph, boiling point is nearly 75 °C

(c) Now from 25 C , draw a line on liquid - vapor region and check where it gets intersected to y-axis.

From graph, vapor pressure = 0.01 ATM

(d) from graph , at temperature 100 C , vapor pressure = 1 atm

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