## Constant pressure in a calorimeter

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

Jielena_Bragasin2G
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### Constant pressure in a calorimeter

Since pressure is always constant in a calorimeter, are all reactions in a calorimeter constant?

jisulee1C
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### Re: Constant pressure in a calorimeter

In a reaction there are variables that change. If the pressure is constant, the temperature or volume or number of moles or other things could be changing. In fact if the pressure is constant it would be an isobaric process where heat could be used to both do work and change the internal energy of the system.

Miriam Villarreal 1J
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### Re: Constant pressure in a calorimeter

A constant-pressure calorimeter measures the change in enthalpy of a reaction occurring in a liquid solution. In that case, the gaseous pressure above the solution remains constant, and we say that the reaction is occurring under conditions of constant pressure.

Tiffany_Chen 2K
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### Re: Constant pressure in a calorimeter

Adding on, for a regular calorimeter, it is constant pressure (air can diffuse in and out). Bomb calorimeter, it is constant volume as it's a sealed container, thus you would use Cv.