Graham's Law:
"Under similar conditions of pressure (partial pressure) the rate of diffusion of different gases is inversely proportional to square root of the density of different gases."
rate of diffusion $r \propto \frac{1}{\sqrt{d}} d=$ density of gas
$r=\text { volume flow rate }=\frac{d V_{\text {out }}}{d t}$
$r=\text { moles flow rate }=\frac{d n_{\text {out }}}{d t}$
$r=$ distance travelled by gaseous molecules per unit time $=\frac{ dx }{ dt }$
The general form of the Grahams law of diffusion shows the variation of rate of diffusion of a gas with pressure of gas, temperature of gas, area of cross-section of orifice and molecular mass of the gas.
Questions —
1. A bottle of dry $NH _{3} \&$ a bottle of dry $HCl$ connected through a long tube are opened simultaneously under identical conditions at both ends. The white ammonium chloride ring first formed will be:
(A) at the centre of the tube
(B) near the $HCl$ bottle
(C) near the $NH _{3}$ bottle
(D) throughout the length of tube
2. At room temperature, $A_{2}$ gas (vapour density $=40$ ) at $1 atm$ pressure and $B_{2}$ gas (vapour density = 10) at $p$ atm pressure are allowed to diffuse through identical pinholes from opposite ends of a glass tube of $1 m$ length and of uniform cross-section. The two gases first meet at a distance of $60 cm$ from the $A_{2}$ end. The value of $p$ is :
(A) $\frac{4}{3} atm$
(B) $\frac{1}{3} atm$
(C) $\frac{3}{4} atm$
(D) $\frac{1}{6} atm$
3. A mixture containing 2 moles of $He$ and 1 mole of $CH _{4}$ is taken in a closed container and made to effuse through a small orifice of container. Then, which is the correct effused volume percentage of $He$ and $CH _{4}$ initially, respectively :
(A) $40 \%, 60 \%$
(B) $20 \%, 80 \%$
(C) $80 \%, 20 \%$
(D) $60 \%, 40 \%$
