Question

At a given temperature, an unknown gas takes 10.0 minutes to travel the distance helium gas travels in 1.66 minutes. What is the approximate molar mass of the unknown gas

Answer 1

The molar mass of the unknown is approximate 145g/mol

Step-by-step explanation:

We can relate the speed of effusion of gases with the molar mass of the 2 compounds using Graham´s law:

`(v_a)/(v_b) =\sqrt{ (m_b)/(m_a) }`

Where V is speed of the gas and m molar mass of a and b gases.

Molar mass of helium is 4g/mol. As the distance of the gases is the same, we can replace the speed of effusion with the time the gas takes to travel the distance. The equation will be:

`(t_b)/(t_a) =\sqrt{ (m_b)/(m_a) }`

Replacing:

`(10.0min)/(1.66) =\sqrt{ (m_b)/(4g/mol) }\\6.024 = \sqrt{ (m_b)/(4g/mol) }\\36.29 = (m_b)/(4g/mol)\\145 g/mol =m_b`

The molar mass of the unknown is approximate 145g/mol