Avogadro's Number And Mole Concept

Solving this uses the mole concept and Avogadro's number as defined in NCERT Class 11, Chapter 13 (Kinetic Theory), where one mole of any substance contains exactly $N_A=6.022\times 10^{23}$ particles. The total number of molecules equals the number of moles multiplied by Avogadro's number, $N=n\times N_A$. Substituting $n=2$ moles gives $N=2\times 6.022\times 10^{23}=1.2044\times 10^{24}$ molecules, approximately $1.2\times 10^{24}$. The option $6.022\times 10^{23}$ corresponds to only one mole, ignoring the factor of two. The option $3.0\times 10^{23}$ mistakenly divides rather than multiplies by the mole count. The option $1.2\times 10^{23}$ has the correct leading digits but the wrong power of ten. A magnitude check reassures us: doubling one mole must double the molecule count, and multiplying $6\times 10^{23}$ by two correctly rolls over into the $10^{24}$ range, so $1.2\times 10^{24}$ is dimensionally and numerically sound.