If 1 gram of each of the following gases is taken at STP, which of the gases will occupy (a) greatest volume and (b) smallest volume?

CO, H2O, CH4, NO


We know that 1 mole of any gas at STP (273K, 1 atm) will occupy 22.4L.


Also the molar weights of CO is 28gm, H2O is 18gm, CH4 is 16gm, NO is 30gm.


Now, 1 gm of these gases will occupy the maximum volume if the molar weight of that gas is the least.


As, volume occupied by 1gm of the gas =


Lesser the molar mass, higher is the volume occupied.


(a) Of all these, CH4 has the least molar mass (16gm), so it would occupy the highest volume for 1gm of the gas.


(b) Similarly, higher the molar mass, lesser is the volume occupied.


Of all these, NO has the highest molar mass (30gm), so it would occupy the least volume for 1gm of the gas.


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