Entropy change due to pressure

[Cristian Carrasco 1F]

When calculating the entropy change in pressure, which R do you use for the formula: nRlnP1/P2?

[Suchita 2I]

It would depend on the units you use in your calculation. The different values of R based on the units are given in the constants and formulas sheet so you can use that to figure it out. So if you take volume in liter, pressure in atm and temperature in kelvin it would be 8.206x10^-2. Make sure all the units are correct and convert to the correct units if required.

[Riya Pathare 2E]

The two common forms of R used are 8.314 J/mol K and 0.08206 L atm/mol K. Which one you use depends on what units the rest of the parts of your equation has.