isothermal reversible vs. isothermal irreversible

[Donovan McGraw 2C]

Why does an isothermal reversible vs. isothermal irreversible system affect the value of delta S total?

[carolineselliott2D]

In a reversible reaction, since it happens so slowly and in “infinite” intervals, the total delta S is equal to 0 because (delta)S surroundings equals the negative of (delta)S system. In a reversible reaction, since the reaction is meant to occur very quickly, the (delta)S surroundings is equal to 0 and (delta)S total = (delta)S system.

[Denise Mora 1C]

Hi, an isothermal reversible process is represented by the equation: delta Ssys = -delta Ssurr. This is because the delta Stotal is set to 0 since any increase in the entropy of the system is balanced by a decrease in the entropy of the surroundings. An isothermal irreversible process involve irreversible changes and lead to an overall increase in entropy.