Question 2.17
NCERT Class XI Physics
One mole of an ideal gas at standard temperature and pressure occupies 22.4 L (molar volume). What is the ratio of molar volume to the atomic volume of a mole of hydrogen ? (Take the size of hydrogen molecule to be about 1 Å). Why is this ratio so large ?
Physical Concept and Assumptions
Assumption 1: hydrogen is an ideal gas so we can use 22.4 liters as the molar volume.
Assumption 2: each hydrogen molecule is a rigid sphere of diameter 1 Å angstorm.
Forces of attraction between two hydrogen atoms are small so they spread as a gas at STP [273.15 K and 100 kPa]. As a result there is a lot of empty space between two atoms of the gas.
What we have to do: We have to compare the sum of volumes of all hydrogen atoms [i.e., if they stay together as a solid] to the volume of the container 22.4 L.
Video Explanation
Please watch this youtube video for a quick explanation of the solution:
Solution in Detail
Vol. of 1 atom
Vol. of 1 mol atom
Why is this ratio so large? Ans: because force of attraction between two hydrogen atoms is small so they spread out as a gas.
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