Question

how to calculate atoms in 0.1 moles of triatoic gas

Answer 1

triatomic gas  means a gas in which number of atoms is three
e.g, if 1 mole of triatomic gas is given then number of mole of atoms = 3 

here ,
number of mole of gas = 0.1 mole 
so, number of mole of atoms = 3 × 0.1 = 0.3 mole 
             but we know, 
1 mole of atoms  = 6.022 × 10²³ atoms 
hence 0.3 mole of atoms = 3 × 6.022 × 10²³
                                         = 18.066 × 10²³ atoms 
                                         =1.8066 × 10²⁴ atoms 

hence, 0.1 mole of triatomic gas = 1.8066 × 10²⁴