Question

number of moles in 128 gm of so2 will be

Answer 1

S = 32, O = 16

Molar mass of SO2 = 32 + 16x2 = 64 g

No. of moles = Given mass/Molar mass
                       = 128/64
                       = 2 moles

Answer 2

Given:
Atomic mass of S=32.06 u
Oxygen=16 u
molecular  mass of SO2=32.06+2x16=64.06g
molar mass of SO2=64.06g/mol
no. Of moles= Given mass/molar mass
=128/64.06=1.99moles