Model 1 – Spontaneous Processes Process Description Change in Enthalpy (H) Chang

Question

Model 1 – Spontaneous Processes Process Description Change in Enthalpy (H) Change in Entropy (S) Spontaneous? A Two pure Homogeneous substances mixture ~ 0 Increasing Yes B Solute on Solute on one side of both sides of membrane membrane ~ 0 Increasing Yes C Polypeptide Individual chain amino acids Exothermic (negative) Increasing (positive) Yes D C3 H8 + 5O2 3CO2 + 4H2 O Exothermic Increasing Yes E 6CO2 + 6H2 O C6 H12O6 + 6O2 Endothermic Decreasing No F Glucose Starch Endothermic Decreasing No G Water Ice Exothermic Decreasing Below 0 °C, yes Above 0 °C, no H Cold water (25 °C) Hot water (60 °C) Endothermic Increasing Below 60 °C, no Above 60 °C, yes

Some of the processes in Model 1 are spontaneous—that is, they will occur without any additional work being done on the system. For example, a solute will diffuse across a membrane until the concentrations of both sides are equal. However, glucose will not spontaneously form from carbon dioxide and water in the atmosphere. The Second Law of Thermodynamics states that a process will be spontaneous when it results in an increase of total entropy in the universe. In other words, either the system or the surroundings must have an increase in entropy, or both. (Please note that the term “spontaneous” does not imply that the change will happen quickly. Rusting is spontaneous under the right conditions, but it can still occur very slowly.)

13. Predict the change in entropy of the surroundings for an endothermic reaction.

Explanation / Answer

Yes, for a process to be spontaneous ,increase of total entropy in the universe is neccessary. In other words, either the system or the surroundings must have an increase in entropy, or both.

Actually the entropy determines the randomness of a system.

Endothermic reactions are those reactions in heat heat is abosored by the system so the temperature decreases. And as in endothermic reaction ,the temperature will go down, the entropy of the surrounding decrease.

For endothermic reactions, enthalpy usually goes up. However, a spontaneous endothermic reaction can occur when the changes in enthalpy and entropy yield a negative Gibbs free energy. An endothermic reaction can be spontaneous if entropy increases by more than the change in enthalpy.

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