As per avagadro hypothesis,
1 mole HI=6.023×1023 number of HI molecules
0.01 mole HI=6.023×1021 number of HI molecules
Quantum yield is defined as
Quantumyield=Molecules decomposedphotons absorbed
photonsabsorbed=MoleculesdecomposedQuantumyield
=6.023×10210.2
=3.0115×1022