Let the moles of Na2CO3 and NaHCO3 be a each.
Meq. of Na2CO3 + Meq. of NaHCO3= Meq. of HCl
a×2×1000+a×1×1000=0.1×V
∴3×a=10−4×V...(i)
Since, mass of mixture =1 g
∴ Mass of Na2CO3 + Mass of NaHCO3=1 g
or a×106+a×84=1
∴a=5.26×10−3...(ii)
From Eqs. (i) and (ii), we get 3×5.26×10−3=10−4×V
or V=157.8 mL
So, the answer is 158 mL.