Solving PV/nRT for T: Temp Needed to Reduce Gas Volume to 2.50L

[fromthepast]

A sample of sulfur hexafluoride gas occupies a volume of 5.10 L at 198 C. Assuming that the pressure remains constant, what temperature (in C) is needed to reduce the volume to 2.50 L?

I used PV/nRT = PV/nRT and got -42 C.

Do I have to convert to Kevlin first and then back to Celsius?

 

[jetwaterluffy]

You would have to convert to Kelvin. Whether to express you answer in Celsius is a matter of prefrence, but your answer will come out in Kelvin.

 

[nasu]

Do I have to convert to Kevlin first and then back to Celsius?

It looks like this is what you did already. You won't get -42 if you use initial temperature in Celsius.