1. Some basic concept of chemistry — Chemistry STD 11 Science — Question

Here, $N_A$ represents Avogadro's number. $M$ represents the molar mass of compound.

Number of molecules present in $36 \,g$ of water $=\frac{36}{18} \times N _{ A }=2\, N _{ A }$

Number of molecules present in $28\, g$ of $CO =\frac{46}{46} \times N _{ A }= N _{ A }$

Number of molecules present in $46 \,g$ of $C _2 H _5 OH =\frac{46}{46} \times N _{ A }= N _{ A }$

Number of molecules present in $54 \,g$ of $N _2 O _5=\frac{54}{108} \times N _{ A }=0.5\, N _{ A }$