The effusion rate of an unknown gas is measured and found to be 31.50 mL/min. Under identical experimental conditions, the effusion rate of O2 is found to be 30.50 mL/min. If the choices are CH4, CO, NO, CO2, and NO2, what is the identity of the unknown gas

Answer : The unknown gas is, NO

Solution :

According to the Graham's law, the rate of effusion of gas is inversely proportional to the square root of the molar mass of gas.

or,

      ..........(1)

where,

= rate of effusion of unknown gas  = 31.50 mL/min

= rate of effusion of gas  = 30.50 mL/min

= molar mass of unknown gas = ?

= molar mass of gas = 32 g/mole

Now put all the given values in the above formula 1, we get:

From the this we conclude that the unknown gas is, NO that has 30.0 g/mol molar mass.

Hence, the unknown gas is, NO

the seeing the electronic configuration we can say that the element is fluorine.

fluorine is the most electronegative element in the periodic table.

but by only seeing the configuration we cannot say about its reactivity because we don't know if its configuration after excitation or by addition of electrons.

but if not then, it is the lightest halogen and exists as a highly toxic pale yellow diatomic gas at standard conditions. as the most electronegative element, it is extremely reactive: almost all other elements, including some noble gases, form compounds with fluorine.