# What is reversible entropy?

## What is reversible entropy?

The second law of thermodynamics states that in a reversible process, the entropy of the universe is constant, whereas in an irreversible process, such as the transfer of heat from a hot object to a cold object, the entropy of the universe increases.

## Why is entropy constant in reversible process?

Entropy remains constant in a reversible process because energy is not “degraded.” It is stored as potential energy in a form that can do enough work to restore the system plus surroundings to their initial conditions. The entropy is merely transferred from system to surroundings.

**Why entropy change for a reversible process is zero?**

Change in entropy for a system undergoing only reversible process may not be necessarily be zero. Now for a reversible process, since the process is really slow we neglect the friction (also called as Internal Irreversibility). Thus Entropy generation = 0.

**Is Delta S 0 for reversible process?**

*In a reversible process the total entropy of a system plus its surrounding is unchanged. delta Suniv = 0.

### Why is entropy always increasing?

Even though living things are highly ordered and maintain a state of low entropy, the entropy of the universe in total is constantly increasing due to the loss of usable energy with each energy transfer that occurs.

### What is the change in entropy for a reversible adiabatic process?

we see that the entropy change of a system during for a reversible, adiabatic process is zero.

**Is entropy 0 for reversible?**

Another form of the second law of thermodynamics states that the total entropy of a system either increases or remains constant; it never decreases. Entropy is zero in a reversible process; it increases in an irreversible process.

**What does it mean if change in entropy is zero?**

Therefore, the entropy change of a system is zero if the state of the system does not change during the process. For example entropy change of steady flow devices such as nozzles, compressors, turbines, pumps, and heat exchangers is zero during steady operation.

## What does it mean when Delta S is negative?

A negative delta S corresponds to a spontaneous process when the magnitude of T * delta S is less than delta H (which must be negative). delta G = delta H – (T * delta S). A negative delta S would mean that the products have a lower entropy than the reactants, which is not spontaneous by itself.

## Why does entropy increase in an irreversible process?

As per second law of thermodynamics, all the spontaneous processes occur in the nature from higher to lower potential. It requires external work to carry out the process against the nature that is from lower to higher potential. Thus all the spontaneous processes are irreversible and they lead to increase in entropy of the universe.

**What is the entropy change for a reversible reaction?**

We know from Equation \\(\\ref{Eq2}\\) that the entropy change for any reversible process is the heat transferred (in joules) divided by the temperature at which the process occurs. Because the conversion occurs at constant pressure, and ΔH and ΔU are essentially equal for reactions that involve only solids, we can calculate the change in entropy for the reversible phase transition where q rev = ΔH.

**Which process involves a decrease in entropy?**

The process that involves a decrease in entropy is water freezing into ice.

### Is a reversible adiabatic process a change in entropy?

An adiabatic process is a process which takes place without transfer of heat (Q = 0). Since the gas does not exchange heat, we have: A reversible adiabatic process is also known as isentropic process, since the entropy of the system does not change.