delta S= q(rev)/ T

[abbydouglas1K]

Under what circumstances do we use this entropy equation ?

[Samantha Kwock 1D]

This entropy equation can be used to calculate the change in entropy when temperature is constant. For example, you can use this equation to calculate the entropy associated with phase changes because they occur at a constant temperature.

[Hai-Lin Yeh 1J]

Note that the equation contains q(rev), where the subscript "rev" on q signified that the energy must be transferred reversibly and in a reversible reaction, temperature is constant. You can also use this equation to work out how to calculate the entropy of vaporization or the entropy of fusion, where q(rev) = deltaH(fusion) or deltaH(vaporization) and T is either melting or boiling point. (This is the phase change that was discussed in the previous comment).

[Krista Mercado 1B]

This equation is used to find the change in entropy for isothermal reversible reactions.

[chrisavalos-2L]

This equation for change in entropy is used when it is a reversible reaction.

[chrisavalos-2L]

This equation for change in entropy is used when it is a reversible reaction.

--- Also when there is no change in temperature (constant temperature)