Question

The number of atoms in $0.25$ mole of a tetra-atomic gas is ( ${N_A}$ = Avogadro number)
(A) 4 ${N_A}$
(B) 2 ${N_A}$
(C) ${N_A}$
(D) 3 ${N_A}$

Answer 1

An atom is the smallest unit of matter that forms chemical elements. Every solid, liquid, gas is composed of atoms. We know that 1 mole consists of ${N_A}$ number of molecules.

Complete Step by step solution:
When four atoms chemically bond together, they form Tetra atomic molecules. Atomicity of tetra atomic compounds is four where atomicity is the total number of atoms present in one molecule of a component, compound, or a substance.
The mole (symbol: mol) is the unit of measurement for quantity of substance in the International System of Units. The mole is widely used in chemistry as a convenient way to tell the quantity of reactants and products of a chemical reaction.
Because tetratomic means, 1 molecule of gas has four atoms each.
Number of moles of atoms is equal to four multiplied by the number of moles of molecules.
Number of moles of atoms $= 4 \times 0.25$
Number of moles of atoms $= 4 \times \dfrac{{25}}{{100}} = 1$
Therefore, the number of atoms in $0.25$ moles of tetra-atomic gas is ${N_A}$ .
Therefore, the correct answer is option C.

Note:
Avogadro's law is an experimental gas law relating the volume of a gas to the amount of substance of gas present. Avogadro's law states at the same temperature and pressure, equal volumes of gases have the same number of molecules. For a given mass of an ideal gas, the moles and volume of the gas are directly proportional if the pressure and temperature are constant.