Does reversible also imply constant T?

[Andie Jian 1D]

I understand that a reversible reaction means that volume and pressure are constantly changing infinitesimally in order to maintain the same pressure inside as outside. However, is temperature also still constant during this reaction, because the change in volume balances out the change in pressure?

[Iona Pay]

If we're talking about expansion of a gas and want to compare the role of temperature in reversible vs irreversible expansions, as we have been in lecture, we could compare these two equations for calculating work:

A. w = -nRTln(V1/V2), for isothermal reversible expansion of a gas.

B. w = -P∆V, for irreversible expansion of a gas at a constant pressure.

In our first equation, T is a constant in the equation for isothermal reversible expansion of a gas - so, we know that it doesn't change (otherwise we would see ∆T). By contrast, T is not directly considered in our second equation; but knowing what we know about expansion of gases at a constant pressure, we know that T must drop in order to allow the gas to expand (∆V), which keeps P constant.

Hope it helps!