Question

One mole of which of the following will have 22.4L at STP (1 bar, 273.15 K)?
(A) $S{O_2}$
(B) $He$
(C) ${H_2}O$
(D) $CC{l_4}$

Answer 1

Hint: The given condition i.e. 1 bar pressure and 0-degree Celsius (273.15 K) temperature are known as Standard Temperature and pressure respectively. STP is used in many thermodynamic calculations. Certain properties of matter such as density, viscosity, boiling point, melting point etc. will vary with changes in temperature or pressure. Having one common set of conditions for calculating these values makes comparisons possible and eases calculations.

Complete step by step solution:
We know the definition of mole i.e. The mole is the unit of measurement for the amount of substance in the International System of Units (SI). A mole of a substance is defined as $6.022 \times {10^{23}}$particles, which may be atoms, molecules, ions, or electrons.
Now, the question asks which molecule/element will have 22.4L volume at STP. This can be decided by the help of Avogadro's hypothesis and molar volume.
You might be thinking what Avogadro's hypothesis is? Let's discuss it.
In 1811, Avogadro explained that the volumes of all gases can be easily determined. Avogadro’s hypothesis states that equal volumes of all gases at the same temperature and pressure contain equal numbers of their particles. Since the total volume that a gas occupies is made up primarily of the empty space between the particles, the actual size of the particles is nearly negligible. A given volume of a gas with small light particles contains the same number of particles as the same volume of a heavy gas with large particles.
Gases are compressible, meaning that when we put them under high pressure, the particles are forced closer to one another. This decreases the amount of empty space between them and thus reduces the volume of the gas. Gas volume is also affected by temperature. When a gas is heated, its molecules move faster since the gas expands. Because of the variation in gas volume due to change in pressure and temperature, the comparison of gas volumes must be done at one standard temperature and pressure. The molar volume of a gas is the volume of one mole of a gas at STP. At STP, one mole of any gas occupies a volume of 22.4 L.
Now, let's have a look at our options. Option (A) and (B) are in a gaseous state at STP whereas option (C) and (D) are in a liquid state at STP. With reference to the above discussion, we know that only gases at STP can have a volume of 22.4 L.

Hence, the answer to the given question is option (A) and (B).

Note: Always remember that with a change in temperature or pressure, the volume of a gas can change for a given number of moles and vice versa. But, the volume of any given gas will be the same for a given volume irrespective of the nature of the gas.