The temperature of a fixed mass of an ideal gas goes from 40ºC to 80ºC at a constant volume. If the initial pressure was x, what is the new pressure?
The mark scheme says it's 2x, but do we use ºC or K in the equation P1/T1 = P2/T2?
The mark scheme says it's 2x, but do we use ºC or K in the equation P1/T1 = P2/T2?
1 Answer
Dec 21, 2017
Celsius.
Explanation:
Given:
#P_1=x# #T_1=40^oC=313K# #T_2=80^oC=353K#
We can see that the temperature is not the same ratio in Kelvin as Celsius, as while 40 is half of 80, 313 is not half of 353.
With Kelvin:
#P_1/T_1=P_2/T_2#
#=>P_2=(P_1T_2)/(T_1)#
#=>P_2=x*353/313#
With Celsius:
#P_1/T_1=P_2/T_2#
#=>P_2=(P_1T_2)/(T_1)#
#=>P_2=x*80/40#
#=>P_2=2x#
So it appears they wanted you to use Celsius.
