What are the Process related to thermodynamids in chemistry?

Answer 1

Yes, but you have to put the energy back into the combustion products. Say you are going green and burning hydrogen. The combustion products are energy and water. You reverse it by passing electricity through the water and reclaiming the hydrogen. The electricity was produced by burning coal to make steam and turn a turbine that turns a generator. You had power loss at each step. You would have been greener to skip the hydrogen step and burn the coal in your car...well, steam engines are a bit messy. Let's turn the burnt coal back into fuel. Carbon burns in air to produce carbon dioxide and energy. Plants take in the carbon dioxide and build sugars, starches and cellulose using the sun's energy to run photosynthesis. Bury those plants and let them cook for a few milennia and they will produce more coal.

Answer 2

Some of the spontaneous causes of irreversible processes in thermodynamics are heat transfer through a finite temperature difference, friction, inelastic deformation, electric flow through a resistance, magnetization or polarization with a hysteresis, unrestrained expansion of fluids, spontaneous chemical reactions, and spontaneous mixing of matter of varying composition or states.

Answer 3

Thermodynamics is a macroscopic science that deals with such properties as pressure, temperature, and volume. Unlike quantum mechanics , thermodynamics is not based on a specific model, and therefore it is unaffected by our changing concepts of atoms and molecules. By the same token, equations derived from thermodynamics do not provide us with molecular interpretations of complex phenomena. Furthermore, thermodynamics tells us nothing about the rate of a process except its likelihood.

Applications of thermodynamics are based on three fundamental laws that deal with energy and entropy changes. The laws of thermodynamics cannot be derived; their validity is based on the fact that they predict changes that are consistent with experimental observations.

The first law of thermodynamics is based on the law of conservation of energy, which states that energy can neither be created nor destroyed; therefore, the total energy of the universe is constant. It is convenient for scientists to divide the universe into two parts: the system (the part of the universe that is under study-for example, a beaker of solution) and the surroundings (the rest of the universe). For any process, then, the change in the energy of the universe is zero. Chemists are usually interested only in what happens to the system. Consequently, for a given process the first law can be expressed as

Δ U = q + w (1)

where Δ U is the change in the internal energy of the system, q is the heat exchange between the system and the surroundings, and w is the work done by the system or performed on the system by the surroundings. The first law is useful in studying the energetics of physical processes, such as the melting or boiling of a substance, and chemical reactions-for example, combustion . The heat change occurring as part of a process is measured with a calorimeter. For a constant-volume process, the heat change is equated to the change in the internal energy Δ U of the system; for a constant-pressure process, which is more common, the heat change is equated to the change in the enthalpy Δ H of the system. Enthalpy H is a thermodynamic function closely related to the internal energy of the system, and is defined as

H = U + PV (2)

where P and V are the pressure and volume of the system, respectively.

The first law of thermodynamics deals only with energy changes and cannot predict the direction of a process. It asks, for example: Under a given set of conditions of pressure, temperature, and concentration, will a specific reaction occur? To answer the question we need a new thermodynamic function called entropy S. To define entropy, we need to use a quantum mechanical concept. The entropy of a system is related to the distribution of energy among the available molecular energy levels at a given temperature. The greater the number of energy levels that have significant occupation, the greater the entropy.

The second law of thermodynamics states that the entropy of the universe increases in a spontaneous process and remains unchanged in an equilibrium process. The mathematical statement of the second law of thermodynamics is given by

Δ S univ = Δ S sys + Δ S surr ≥ 0 (3)

where the subscripts denote the universe, the system, and the surroundings, respectively. The greater than portion of the "greater than or equal to" sign corresponds to a spontaneous process, and the equal portion corresponds to a system at equilibrium. Because processes in the real world are spontaneous, the entropy of the universe therefore constantly increases with time.

As is not the case with energy and enthalpy , it is possible to determine the absolute value of entropy of a system. To measure the entropy of a substance at room temperature, it is necessary to add up entropy from the absolute zero up to 25°C (77°F). However, the absolute zero is unattainable in practice. This dilemma is resolved by applying the third law of thermodynamics, which states that the entropy of a pure, perfect crystalline substance is zero at the absolute zero of temperature. The increase in entropy from the lowest reachable temperature upward can then be determined from heat capacity measurements and enthalpy changes due to phase transitions.

Because it is inconvenient to use the change in entropy of the universe to determine the direction of a reaction, an additional thermodynamic function, called the Gibbs free energy ( G ), is introduced to help chemists to focus only on the system. The Gibbs free energy of a system is defined as G = H − TS , where T is the absolute temperature. At constant temperature and pressure, Δ G is negative for a spontaneous process, is positive for an unfavorable process, and equals zero for a system at equilibrium. The change in Gibbs free energy can be related to the changes in enthalpy and entropy of a reaction, and also to the equilibrium constant of the reaction, according to the equation Δ G ° = − RT ln K , where Δ G° is the change in Gibbs free energy under standard-state conditions (1 bar), R is the gas constant, and K is the equilibrium constant.

Answer 4

Photosynthesis is reversible, if you burn for example glucose you get energy in form of light or heat and CO2. With breathing itself we partially reverse the photosynthesis since we convert oxygen and sugar to carbon dioxide.

Answer 5

A reversible process is one in which entropy doesn't increase. In other words, it should be possible to go through the process, and then to reverse the process (go through the process in reverse order), without using any energy.Note that this is an idealization; in general, REAL processes may approach a reversible process, but usually they won't be 100% reversible - some energy is wasted when going "back and forth".

Answer 6

Yes, combustion is an oxidation reaction, so its reverse would be a redox reaction. For example, 2H2O + CO2 ---> 2O2 +CH4.

Answer 7

Ideal Carnot Cycle is one example

It is a process that does not have an energy loss.

Answer 8

temperature ,pressure .gibbs absorption energy, entropy, entholphy

Answer 9

Many metabolic reactions are reversible, and I don't think all metabolisms reactions are reversible.

Answer 10

Yes, a liquid can become a solid again through solidification or freezing.