Question

The temperature in _______ scale is always positive.

Answer 1

At zero Kelvin temperature, the molecules are unable to move and all the disorder disappears. Thus, a molecule cannot have a lower temperature than absolute zero on the kelvin scale. We cannot go lower than absolute zero temperature.

All the gas laws follow the Kelvin scale because pressure and volume depend on the kinetic energy of the molecules. Kinetic energy is proportional to kelvin temperature.

If we want to calculate $\frac{PV}{RT}$ by using the Celcius scale, then it is not valid.

So, the correct answer is kelvin.