0.221 moles
Number of moles = Mass ÷ Molar mass
In this case;
Mass of C6H10S = 25.2 g
Molar mass of C6H10S = 114.21 g/mol
Therefore;
Number of moles of C6H10S = 25.2 g ÷ 114.21 g/mol
= 0.221 moles
Hence, the number of moles in 25.2 g of C6H10S is 0.221 moles