20cm3 of an unknown gas Q takes 12.6 seconds to pass through small orifice.10cm3 of
oxygen gas takes 11.2 seconds to diffuse through the same orifice under the same
conditions of temperature and pressure .Calculate the molecular mass of unknown gas Q
( O=16)
To calculate the molecular mass of unknown gas Q, we can use Graham's law of effusion:
(Gas Q rate/Gas O rate) = √(Molar mass of Gas O/Molar mass of Gas Q)
Given:
Volume of Gas Q = 20 cm³
Rate of Gas Q = 20 cm³/12.6 s = 1.59 cm³/s
Volume of Gas O = 10 cm³
Rate of Gas O = 10 cm³/11.2 s = 0.89 cm³/s
Using the formula, we get:
(1.59/0.89) = √(32 / x)
Solving for x, we get:
x = 32 / (1.59/0.89)²
x = 32 / (1.786)²
x = 32 / 3.188
x = 10.04
Therefore, the molecular mass of unknown gas Q is 10.04 g/mol.