Explanation:
(1) 4 mol of \({\rm{He}} = 4 \times 6.022 \times {10^{23}}\,{\rm{He}}\) atoms
(2) \({\rm{4}}\,{\rm{u}}\,\,{\rm{of }}\,{\rm{He = }}\frac{{{\rm{4u}}}}{{{\rm{4u}}}}{\rm{ = 1He}}\) atom
\[\begin{array}{l}
{\rm{4g}}\,{\rm{of}}\,{\rm{Helium}} = \frac{{4\;{\rm{g}}}}{{4\;{\rm{g}}}}{\rm{mole}} = 1{\rm{mole}}\\
= 6.022 \times {10^{23}}{\mkern 1mu}\, {\rm{He}}\,{\rm{atoms}}.
\end{array}\]
(4) 2.2710982 L of He at STP
\(=\dfrac{2.271}{22.710982}\) mole
\(=0.1\) mole (or) \(6.022 \times 10^{22} \,\mathrm{He}\) atoms.