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12 -- Part 3: Intermolecular Forces: Liquids and Solids
As a result of a chemical reaction, 0.132 g H2O is produced and maintained at a temperature of 50.0 degC in a closed flask of 525 mL volume.
Let's take a look at the three possibilities in order.
A 0.132 g sample of H2O has a volume of less than 0.13 mL.
The sample couldn't fill a 525 mL flask.
The portion of the flask that is not occupied by liquid water must be filled with something.
That is water.
If the entire 0.132 g H2O were present in the gaseous state, the ideal gas equation would be used to calculate the pressure that would be exerted.
The vapor pressure of water is 50.0 degC.
The calculated pressure is greater than the vapor pressure.
The water formed in the reaction when H2O(g) condenses to H2O(l) is the pressure at which the liquid and vapor are in equilibrium.
The final condition in the flask is only possible with this.
Liquid water and water vapor are in equilibrium.
The solution to this problem was found through the application of the ideal gas equation and understanding of vapor pressure.
In the first two steps, we considered the two extremes, the first being liquid water and the second being all vapor.
Figure 18 is not likely to be found if you look for vapor pressure data on a liquid in a handbook or data tables.
Table 12.5 is unlikely to be found with the exception of water and mercury.
You will find mathematical equations about temperatures and vapor pressures.
The data can be summarized in one line.
A common form of vapor pressure equation is Equation (12.1).
The mercury is expressed in the natural logarithm and the temperatures are in the Kelvin.
The point is marked by a black arrow.
Data from Tables 12.4 and 12.5 can be used to calculate the vapor pressure of water.
The Clausius-Clapeyron equation requires four pieces of data to be analyzed.
We need two temperatures, a pressure, and the enthalpy of vaporization to calculate a vapor pressure.
Let's assume that the value given in Table 12.4 applies throughout the temperature range from 30.0 degC to 40.0 degC.
Determine that e 0.28 is 1.32.
If we want to check our answer, we can use the known pressure to see if we get the pressure given in the problem.
We can check this against the Vapor Pressure of water at 35.0 degC, which is 42.175mmHg.
The vapor pressure of methyl alcohol is listed in a handbook.
During boiling, the energy absorbed as heat is used to convert the molecule on the stove to a liquid.
As the water begins to warm, the temperature stays constant until all the liquid has bubbles.
All the boiling point is the boiling point of a liquid at 1 atm pressure.
An empty paper cup quickly ignites.
If a paper cup is filled with water, it can be heated for a long time.
Because of the high heat capacity of water, the temperature of the water and cup is kept well below that required for the paper to be burned.
The liquid needs to be converted to its vapor.
The barometric pressure was slightly below the boiling point of 99.9 degC.
The boiling point of a liquid varies on the summit of Mt.
The new points of intersection will be able to heat a cup of tea at different temperatures if the dashed line is shifted.
The barometric pres is 70 degrees.
The barometric pressure is 630mmHg at an altitude of 1609 m. The boiling point of water is 1203 degrees.
It takes longer to cook food at lower boiling point temperatures.
A three-minute boiled egg takes longer than three minutes to cook.
The effect of high altitudes can be counteracted by using a pressure cooker.
In a pressure cooker, the cooking water is maintained under higher-than-atmospheric pressure and the boiling temperature increases to 120 degrees.
There are bubbles that form tinuously.
Many times atmospheric pressure can be attained.
The density of the liquid decreases, the vapor increases, and even be used exclusively.
The surface tension of the liquid is zero.
The critical temperature is Tc and the critical pressure is Pc.
The highest point on a vapor pressure curve is the critical point.
Table 12.6 contains critical temperatures and pressures.
This liquefaction can be accomplished by applying enough pressure.
The liquefaction of gases will be commented on on page 542.
You would expect their boiling points to increase if they were placed in the order in which they are.
Intermolecular forces are related to boiling point trends.
The types and strengths of intermolecular forces should be identified.
There are three substances that are nonpolar.
The strengths of dispersion forces should increase with increasing molecular mass.
The molecule of ClNO is polar and has a mass similar to that of Cl2 The higher boiling point for ClNO suggests stronger intermolecular forces.
We should not expect the boiling point of ClNO to be higher than that of CCl4 because of the large difference in their molecular mass.
The expected order is N2 6.
Even though one molecule is polar, it does not have the highest boiling point, which indicates that dispersion forces can be stronger than dipole-dipole forces.
The expected order of increasing boiling point is Ne, He, 1CH322CO, O2, O3.
At the beginning of the text, we mentioned some of the properties of the material.
We will talk about some properties that allow us to think of solids in relation to the other states of matter.
There is a regular arrangement of particles.
The particles could be atoms, ion, or molecule.
When a solid is heated, it vibrates more vigorously.
The ordered structure is disrupted when a temperature is reached.
The atoms can slip past one another and cause the solid to lose its shape and be converted to a liquid.
The melting point of a solid is the same as the freezing point.
When we add heat uniformly to a solid-liquid mixture at equilibrium, the temperature remains constant.
The temperature begins to rise when all the solid has melted.
The liquid freezes at a constant temperature if we remove heat uniformly from a solid-liquid mixture.
The enthalpies of fusion are expressed in kilojoules per mole.
The most well-known example of a melting 0 8C point is that of water.
Liquid and solid water in contact with air and under standard atmospheric pressure are in equilibrium.
It is easy to determine the freezing point of a liquid.
Measure the liquid temperature when the broken-line portion cools.
As the solid cools, the temperature is free to fall again.
The process can be run backwards if we start with the solid and add heat.
While melting occurs, the temperature remains constant.
A cooling curve that has been flipped from left to right is the appearance of the heating curve.
The temperature can drop below the freezing point.
Examples of supercooled nucleation events must occur in order for a solid to form.
Water droplets in the sky can be classified as a nucleation event.
Homogeneous nucleation is when a small region of the liquid becomes a crystal.
When they involve the formation of a small crystal on the surface of an inert particle, or on scratches on the container, for example, to find a bit of dust.
The liquid may turn to ice if they can nucleate the droplets.
When a supercooled liquid begins to freeze, the temperature goes back to the normal freezing point.
A cooling curve just before the horizontal portion can be seen as supercooling.
Solids are not as volatile as liquids at a given temperature because of the stronger intermolecular forces present.
A dynamic equilibrium exists between a solid and its liquid.
Dry ice and ice have significant pressures.
If you live in a cold climate, you are aware that snow can disappear from the ground even if the temperature doesn't rise.
The snow does not melt under these conditions.
The ice has a pressure of 4.58mmHg.
The solid ice has a Vapor Pressure of 4.58mmHg.
The ice will form if the air is not saturated with water vapor.
The Focus On feature for Chapter 6, Earth's Atmosphere, at www.masteringchemistry.com, discusses the topic of dew and frost formation.
Imagine constructing a pressure-temperature graph in which each point on vapor is produced at about the graph represents a condition under which a substance might be found.
Liquid of temperature and pressure can be either single phases or states of matter or as two or more phases in equilibrium with one another.
The parts of the diagram correspond to sin Pressure, gle phases, or states of matter.
Two phases in equilibrium are represented by gas adjoin regions.
The red points show the temperatures and pressures of the gas.
The triple at which solid is stable is 113.6 degC and 91.6mmHg.
The blue points are the temperatures at which a line at P is the temperatures and intersects the fusion and vapor pressure curves.
The normal melting point and triple point are almost the same temperature as the limited range pressure of 91.6mmHg.
The slope of the line is determined by C/subH.
The melting point solid CO2 is heated in an open container and it gets away from a constant temper and triple point temperatures.
It doesn't produce a liquid by the same because it maintains a low temperature.
Dry ice is often used in freezing and preserving food.
There are three states of matter involved in the action of the fire extinguishers.
equilibrium temperatures are the liquid CO2's temperature.
A blanket of CO21g2 can be used around the fire to help quench it.
It is difficult to know what to call the state of matter at temperatures and pressures above the critical point because the liquid and gaseous states are indistinguishable.
This state of matter has a high density of a liquid and low viscosity of a gas.
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