##### Asked by: Katty Warner

**If the total entropy change is positive, the process is a spontaneous process**. If the total entropy change is negative, the process is a non-spontaneous process. A process will be spontaneous when the randomness of the molecules present in the system increases.

## How does total entropy change for a spontaneous process?

Thus, the Second Law of Thermodynamics can be stated as: For a spontaneous process, **the total entropy of the system plus the surroundings increases**. Entropy is quite different from energy: it is not conserved, i.e., entropy can be created during chemical or physical changes.

## What is the entropy of a spontaneous reaction?

Predicting the spontaneity of a reaction

For a spontaneous process, the total entropy change, **ΔS _{total} is always greater than zero**. Also, for a spontaneous process, the total change in entropy is 0, i.e. ΔS

_{total}> 0.

## What is the value ∆ G ∆ s for spontaneous reaction?

**A negative value for ΔG indicates a spontaneous process**; a positive ΔG indicates a nonspontaneous process; and a ΔG of zero indicates that the system is at equilibrium.

## Does a spontaneous reaction has positive total change in entropy?

A reaction will be spontaneous if the change in G , ΔG , is negative. For the product of temperature times ΔS , where ΔS is the change in entropy, **if the change in entropy is positive (disorder increases), then TΔS , when subtracted, becomes negative**.

## What is the condition for spontaneous reaction?

The free energy change for the spontaneous reactions is as follows. For spontaneous reactions the free energy change is always negative. The reaction is spontaneous if $\Delta G < 0$.

## What is true of spontaneous reactions?

What is true of spontaneous reactions? **They are instantaneous**. They are indicated by a negative change in Gibbs free energy.

## Which of the following will have a ΔS 0?

Free Energy and Thremodynamics

Question | Answer |
---|---|

Which of the following processes have a ΔS>0? | potassium iodide dissolves in pure water |

Which of the following processes have a ΔS<0? | water freezes, methyl alcohol condenses, propanol (g, at 555 K) –> propanol (g, at 400 K) CO2 (g) –> CO2 (s) |

## When G 0 is a spontaneous reaction?

If ΔG<0, the process occurs spontaneously, that is, it proceeds in the forward direction, as written, until it reaches equilibrium. **If ΔG=0, the system is at equilibrium**. If ΔG>0, the process is not spontaneous as written but occurs spontaneously in the reverse direction, until it reaches equilibrium.

## Is positive delta G spontaneous?

Reactions with a negative ∆G release energy, which means that they can proceed without an energy input (are spontaneous). In contrast, reactions with a positive ∆G need an input of energy in order to take place (are **non-spontaneous**).

## Which combination of ΔH and ΔS never has a spontaneous reaction?

When **ΔH is positive and ΔS is negative**, the sign of ΔG will always be positive, and the reaction can never be spontaneous.

## Under what conditions is S 0 for a spontaneous process?

When ΔS > 0 and ΔH > 0, the process will be spontaneous at **high temperatures** and non-spontaneous at low temperatures. When ΔS < 0 and ΔH < 0, the process will be spontaneous at low temperatures and non-spontaneous at high temperatures.

## Does entropy determine spontaneity?

We can assess the spontaneity of the process by calculating the entropy change of the universe. If ΔS_{univ} is positive, then the process is spontaneous.

Connecting Entropy and Heat to Spontaneity.

ΔSuniv>0 | spontaneous |
---|---|

ΔSuniv<0 | nonspontaneous (spontaneous in opposite direction) |

## Why Does entropy increase in spontaneous reactions?

**If heat flows into the surroundings (i.e., when a reaction is exothermic) the random motions of the molecules in the surroundings increase**. Thus, the entropy of the surroundings increases. The second law of thermodynamics states that the total entropy of the universe always increases for a spontaneous process.

## What does ΔS stand for?

Delta S is a term used to denote the **total change in entropy**. Entropy is a measure of the degree of randomness or the degree of disorder in a given system. Therefore, if the entropy of the system increases after a certain event, the value of delta S will be positive.

## Is entropy always increasing?

**Entropy always increases**, because a high amount of disorder is, by definition, is more likely than a low amount of disorder. With our definition of disorder as the multiplicity of the macrostate, every condition of a system has a well-defined disorder.

## Which combination of ΔH and ΔS never has a spontaneous reaction?

When **ΔH is positive and ΔS is negative**, the sign of ΔG will always be positive, and the reaction can never be spontaneous.

## Is negative entropy spontaneous?

If a reaction is exothermic ( H is negative) and the entropy S is positive (more disorder), the free energy change is always negative and the reaction is always spontaneous.

Enthalpy | Entropy | Free energy |
---|---|---|

endothermic, H > 0 | decreased disorder, S < 0 | reaction is never spontaneous, G > 0 |

## What happens when Delta H is positive and Delta S is negative?

Gibbs free energy relates enthalpy, entropy and temperature. **A spontaneous reaction will always occur when Delta H is negative and Delta S is positive**, and a reaction will always be non-spontaneous when Delta H is positive and Delta S is negative.