Question
The temperature of an open room of volume 30 m3 increases from 17°C to 27°C due to sunshine. The atmospheric pressure in the room remains 1 × 105 Pa. If ni and nf are the numbers of molecules in the room before and after heating, then nf – ni will be
-
2.5 x 1025
-
-2.5 x 1025
-
-1.61 x 1023
-
1.38 x 1023
Solution
B.
-2.5 x 1025
Using ideal gas equation
PV = nRT
(N is number of moles)
P0V0 = niR × 290 ...... (1)
[Ti = 273 + 17 = 290 K]
After heating
P0V0 = NfR × 300 ...... (2)
[Tf = 273 + 27 = 300 K]
from equation (1) and (2)
putting P0 = 105 PA and V0 = 30 m3
Number of molecules nf – ni = – 2.5 × 1025
