Answer: 1.41725 X 10^{24} atoms
Explanation:
One male of any gas containing no. of atoms[tex]$=6.023\times10^{23}$[/tex]
2.5 moles of gas containing no. of atoms[tex]$=2.5\times6.023\times10^{23}$=15.0575\times10^{23}$[/tex]
The given gas is triatomic gas. Hence
No. of atoms[tex]$=3\times15.075\times10^{23}$[/tex]
[tex]$=14.1725\times10^{23}$\\$=1.41725\times10^{24}$[/tex]