✔ 最佳答案
1. Using iseal gas equation PV/T = constant
hence, (1 x Vo)/273 = 2 x V/(273+85)
where Vo and V are the initial and final volume of the gas
hence, V/Vo = (273+85)/(2 x 273) = 0.656
Percentage change in volume
= [(V - Vo)/Vo] x 100% = [(V/Vo - 1)] x 100% = (0.656-1) x 100% = -34.4%
The gas has reduced in volume by 34.4%
2. Since molar mass of helium = 4 g/mol, and 1 mole of any gas occupies 22.4 L at STP (Avogadro's hypothesis)
Volume of 1 mole of gas at 25'C, using ideal gas law, is= [(273+25)/273] x 22.4 L = 24.45 L = 0.0245 m^3
Density of gas at 25'C = 4/0.0245 g/m^3 = 163.26 g/m^3 = 0.163 kg/m^3
hence, rms speed = square-root[3 x pressure/density]i.e. rms speed = square-root[ 3 x 10^5/0.163] m/s = 1357 m/s
