Define degrees of freedom - phase rule and phase diagrams, Chemistry

Assignment Help:

Define Degrees of freedom - phase rule and phase diagrams?

Consider a system in an equilibrium state. In this state, the system has one or more phases; each phase contains one or more species; and intensive properties such as T, p, and the mole fraction of a species in a phase have definite values. Starting with the system in this state, we can make changes that place the system in a new equilibrium state having the same kinds of phases and the same species, but different values of some of the intensive properties. The number of different independent intensive variables that we may change in this way is the number of degrees of freedom or variance, F, of the system. Clearly, the system remains in equilibrium if we change the amount of a phase without changing its temperature, pressure, or composition.

This, however, is the change of an extensive variable and is not counted as a degree of freedom. The phase rule, in the form to be derived, applies to a system that continues to have complete thermal, mechanical, and transfer equilibrium as intensive variables change. This means different phases are not separated by adiabatic or rigid partitions, or by semipermeable or impermeable membranes. Furthermore, every conceivable reaction among the species is either at reaction equilibrium or else is frozen at a fixed advancement during the time period we observe the system. The number of degrees of freedom is the maximum number of intensive properties of the equilibrium system we may independently vary, or fix at arbitrary values, without causing a change in the number and kinds of phases and species. We cannot, of course, change one of these properties to just any value whatever. We are able to vary the value only within a certain finite (sometimes quite narrow) range before a phase disappears or a new one appears. The number of degrees of freedom is also the number of independent intensive variables needed to specify the equilibrium state in all necessary completeness, aside from the amount of each phase. In other words, when we specify values of F different independent intensive variables, then the values of all other intensive variables of the equilibrium state have definite values determined by the physical nature of the system. Just as for a one-component system, we can use the terms bivariant, univariant, and invariant depending on the value of F.


Related Discussions:- Define degrees of freedom - phase rule and phase diagrams

Filling of electron according to aufbau''s principle, According  to Aufbau...

According  to Aufbau's principle, which of the three 4d, 5p  and  5s will be filled with electrons first: (1) 4d (2) 5d (3) 5s (4) 4d and 5s  will be filled simultaneo

Solid state: silver density, Silver has a density of 10.5gcm -3 . The no. ...

Silver has a density of 10.5gcm -3 . The no. of silver atoms on a surface area of 10-12m 2 can be expressed in scientific notation aas y x 10x.The value of x is ..? Ans) d = m

Wave, #quesdcsxxdxf tion..

#quesdcsxxdxf tion..

Tests for acetone - indigo test and iodoform test, Tests for acetone - Indi...

Tests for acetone - Indigo test and Iodoform test (a) Indigo test: When a small amount of orthonitrobenzaldehyde is added to approximately 2 ml. of acetone and it is diluted al

Describe structure of solids, Q. Describe Structure of Solids? Ans. ...

Q. Describe Structure of Solids? Ans. Solids are different from gases and liquids because they have a fixed shape. This definite shape occurs as the individual particles w

Preservatives - chemicals in food, Preservatives: The preservatives av...

Preservatives: The preservatives avoid spoilage of food because of microbial expansion. The most common preservative employed is sodium benzoate; C 6 H 5 COON a It is metabol

Acidity determination, 20ml of water sample requires 15ml of 0.1mg/l sodium...

20ml of water sample requires 15ml of 0.1mg/l sodium carbonate using phenolphthalein indicator. state the type of acidity and calculate the acidity

Periodic table, how periodic table is helpful in chemistry give two example...

how periodic table is helpful in chemistry give two example

What are the primary factors of influence solubility, Q. What are the prima...

Q. What are the primary factors of influence solubility? Ans. Solubility is the extent to which a solute dissolves in a solvent. Solutions that have larger quantities of

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd