Can entropy be zero? How do free energy and entropy relate? When does entropy increase? What is the difference between entropy and enthalpy? See all questions in Entropy. Top Chemistry Educators Lizabeth T. Numerade Educator. Stephen P. Drexel University. Allea C. University of Maryland - University College. Jacquelin H. Brown University. Chemistry Bootcamp Lectures Intro To Chem - Introduction Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties.
Classification and Properties of Matter In chemistry and physics, matter is any substance that has mass and takes up space by having volume. Recommended Videos For each pair of substance….
For each pair, tell which …. Which of the following ele…. Which gas would you expect…. Share Question Copy Link. Need the answer? Create an account to get free access. Sign Up Free. Log in to watch this video Skip to content Which of the following States has the greatest entropy? The answer is a Solid. What is entropy unit? Which h2o has the greatest entropy? As water vapours have highest entropy , and liquid water has more entropy than the ice. Can entropy be negative? Does higher entropy mean more stable?
Which gas has highest entropy? What is entropy dependent on? What causes increase in entropy? In which state entropy is maximum? Thermodynamically, equilibrium is the state of maximum entropy minimum energy. What is another name for the first law of thermodynamics? What change in entropy is favorable? What is entropy example? Is entropy the same as chaos? What is another word for entropy? At absolute zero the situation is very simple; no thermal energy is available to bring about dissociation, so the only component present will be dihydrogen.
The result is exactly what the LeChatelier Principle predicts: the equilibrium state for an endothermic reaction is shifted to the right at higher temperatures. This combustion reaction , like most such reactions, is spontaneous at all temperatures. The positive entropy change is due mainly to the greater mass of CO 2 molecules compared to those of O 2. The decrease in moles of gas in the Haber ammonia synthesis drives the entropy change negative, making the reaction spontaneous only at low temperatures.
Thus higher T , which speeds up the reaction, also reduces its extent. Dissociation reactions are typically endothermic with positive entropy change, and are therefore spontaneous at high temperatures. Ultimately, all molecules decompose to their atoms at sufficiently high temperatures. This reaction is not spontaneous at any temperature , meaning that its reverse is always spontaneous.
But because the reverse reaction is kinetically inhibited, NO 2 can exist indefinitely at ordinary temperatures even though it is thermodynamically unstable. Everybody knows that the solid is the stable form of a substance at low temperatures, while the gaseous state prevails at high temperatures. Why should this be? Changes of phase involve exchange of energy with the surroundings whose energy content relative to the system is indicated with much exaggeration!
When solid and liquid are in equilibrium middle section of diagram below , there is sufficient thermal energy indicated by pink shading to populate the energy states of both phases. If heat is allowed to flow into the surroundings, it is withdrawn selectively from the more abundantly populated levels of the liquid phase, causing the quantity of this phase to decrease in favor of the solid.
The temperature remains constant as the heat of fusion is returned to the system in exact compensation for the heat lost to the surroundings. Finally, after the last trace of liquid has disappeared, the only states remaining are those of the solid.
Any further withdrawal of heat results in a temperature drop as the states of the solid become depopulated. Vapor pressure lowering, boiling point elevation, freezing point depression and osmosis are well-known phenomena that occur when a non-volatile solute such as sugar or a salt is dissolved in a volatile solvent such as water.
The key role of the solvent concentration is obscured by the greatly-simplified expressions used to calculate the magnitude of these effects, in which only the solute concentration appears. The details of how to carry out these calculations and the many important applications of colligative properties are covered elsewhere.
Our purpose here is to offer a more complete explanation of why these phenomena occur. Basically, these all result from the effect of dilution of the solvent on its entropy, and thus in the increase in the density of energy states of the system in the solution compared to that in the pure liquid. Equilibrium between two phases liquid-gas for boiling and solid-liquid for freezing occurs when the energy states in each phase can be populated at equal densities.
The temperatures at which this occurs are depicted by the shading. Dilution of the solvent adds new energy states to the liquid, but does not affect the vapor phase. This raises the temperature required to make equal numbers of microstates accessible in the two phases. Dilution of the solvent adds new energy states to the liquid, but does not affect the solid phase. This reduces the temperature required to make equal numbers of states accessible in the two phases.
The ideal gas law is easy to remember and apply in solving problems, as long as you get the proper values a. The pressure acts to compress the liquid very slightly, effectively narrowing the potential energy well in which the individual molecules reside and thus increasing their tendency to escape from the liquid phase. In terms of the entropy, we can say that the applied pressure reduces the dimensions of the "box" within which the principal translational motions of the molecules are confined within the liquid, thus reducing the density of energy states in the liquid phase.
Applying hydrostatic pressure to a liquid increases the spacing of its microstates, so that the number of energetically accessible states in the gas, although unchanged, is relatively greater— thus increasing the tendency of molecules to escape into the vapor phase. In terms of free energy, the higher pressure raises the free energy of the liquid, but does not affect that of the gas phase. This phenomenon can explain osmotic pressure.
Osmotic pressure, students must be reminded, is not what drives osmosis, but is rather the hydrostatic pressure that must be applied to the more concentrated solution more dilute solvent in order to stop osmotic flow of solvent into the solution. Chem1 Virtual Textbook. Learning Objectives You are expected to be able to define and explain the significance of terms identified in bold.
A reversible process is one carried out in infinitessimal steps after which, when undone, both the system and surroundings that is, the world remain unchanged see the example of gas expansion-compression below. Although true reversible change cannot be realized in practice, it can always be approximated.
As a process is carried out in a more reversible manner, the value of w approaches its maximum possible value, and q approaches its minimum possible value. The entropy of a substance increases with its molecular weight and complexity and with temperature.
The entropy also increases as the pressure or concentration becomes smaller. Entropies of gases are much larger than those of condensed phases.
Reversible and irreversible changes A change is said to occur reversibly when it can be carried out in a series of infinitesimal steps, each one of which can be undone by making a similarly minute change to the conditions that bring the change about. Definition: Reversible Changes A reversible change is one carried out in such as way that, when undone, both the system and surroundings that is, the world remain unchanged.
The impossibility of extracting all of the internal energy as work is essentially a statement of the Second Law. The physical meaning of entropy Entropy is a measure of the degree of spreading and sharing of thermal energy within a system. The cooler block contains more unoccupied microstates, so heat flows from the warmer block until equal numbers of microstates are populated in the two blocks. A gas expands isothermally to twice its initial volume.
The increased thermal energy makes additional microstates accessible. The increase is by a factor of about 10 20,,,,, ,, Equal volumes of two gases are allowed to mix.
The effect is the same as allowing each gas to expand to twice its volume; the thermal energy in each is now spread over a larger volume. One mole of dihydrogen, H 2 , is placed in a container and heated to K. Some of the H 2 dissociates to H because at this temperature there are more thermally accessible microstates in the 2 moles of H.
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