Chemistry
posted by danny123 .
A sample of gas confined in a cylinder with a movable piston is kept at constant pressure. The volume of the gas doubles when the temperature of the gas is changed from
a. 200. K to 400. K
b. 200. C to 400. C
How do you know if it's kelvin or celsius?
k= c + 273, by the way.

You solve the problem which ALWAYS comes out in Kelvin because you may use ONLY Kelvin in the solution. The volume doubles when the Kelvin T doubles and is halved when the Kelvin T is halved.
Doubling the celsius, by the way, will NOT double the volume and you can prove that by the following:
Suppose we let V1 = 10 mL, then
(V1/T1) = (V2/T2)
(10/20 K) = (V2/40 K)
V2 = 10mL*(40/20 = 20 mL (double T doubles V) BUT
from 20 celsius to 40 celsius is from 293 K to 313 K and
(10/293) = (V2/313)
V2 = 10 mL*(313/293) = 10.7 mL. See. Not even close. 
thanks