## Reversible vs. Irreversible

$w=-P\Delta V$
and
$w=-\int_{V_{1}}^{V_{2}}PdV=-nRTln\frac{V_{2}}{V_{1}}$

Sydney Pell 2E
Posts: 100
Joined: Wed Sep 11, 2019 12:17 am

### Reversible vs. Irreversible

What makes an expansion reversible vs irreversible?

LNgo 1G
Posts: 100
Joined: Sat Aug 24, 2019 12:16 am

### Re: Reversible vs. Irreversible

An expansion is reversible when temperature is constant, but pressure and volume are variables; it is irreversible when pressure is constant and temperature changes.

MaryBanh_2K
Posts: 101
Joined: Wed Sep 18, 2019 12:21 am

### Re: Reversible vs. Irreversible

An expansion is reversible when the temperature is constant. This process is gradual and requires more work. It is reversible because everything is at equilibrium and therefore entropy is equal to zero. During a reversible expansion, work is negative and the system is losing energy by expanding; however, the lost energy is being replaced by the surrounding heat which is why q is positive. On the other hand, expansion is irreversible when pressure is constant. This process occurs spontaneously and suddenly, so it requires less work and entropy is greater than zero.

805312064
Posts: 50
Joined: Thu Jul 11, 2019 12:16 am

### Re: Reversible vs. Irreversible

Reversible reactions are always at equilibrium (entropy = 0) because all energy lost from expansion is replaced by the surrounding heat! In contrast, irreversible reactions occur quickly - too quickly for the energy to be replaced.