Internal energy of an isothermal reaction

[Erika Patel 3I]

Why is the of an isothermal reaction equal to 0? I thought that isothermal would just mean that q=0, but this isn't the case in the entropy problems that we solved.

[Nancy Duenas Dis 1D]

Hi! In an isothermal reaction, the temperature remains constant throughout the process. Since entropy (ΔS) is a measure of the randomness or disorder of a system and is defined as the change in heat (q) divided by the temperature (T), if the temperature doesn't change (T = constant), then the change in entropy (ΔS) is zero. This means that for an isothermal reaction, ΔS = 0. Hope this helps!