Question

Q1)A sample of N2O Effuses from a container in 42 seconds .how long will it take the same amount of gaseous I2to Effuse from the same container under identical conditions?

Q2)calculate the root mean square velocity and kinetic energy of F2,Cl2and Br2 at 298K.

•rank the 3 halogens with respect to their rate of effusion.

Answer 1

According to Graham's Law of diffusion
r1/r2 = SQRT(M2/M1)
Let here
r1 = Rate of diffusion of I2 = ?
r2 = Rate of diffusion of N2O = 42 s
M1 = Molar mass of I2 = 254 g/mol
M2 = Molar mass of N2O = 44 g/mol
Thus
r1 = r2 x (M2/M1)^1/2 = 42 x (254/44)^1/2 = 100.91sec

2. The root mean square velocity of gas molecules as a function of temperature is (M is molecular weight):
v²rms = 3RT/M,
and kinetic energy is given by:
KE = ½Mv ²
We can make the substitution:
KE = ½M3RT/M, or
KE = (3/2)RT.
Notice the molecular weight variable is gone; that means the answer will be the same for F2, Cl2, and Br2:
KE = (3/2) (8.314 J/K*mole) (298 K) = 3716 J/mole.