On heating NaHCO3 decomposes to gives CO2
2NaHCO3→Na2CO3+H2O+CO2↑
Meq of NaHCO3=Meq of CO2
(wNaHCO3×1000)/84 = (56/22400)×2×1000
wNaHCO3=0.42g in 2.0g mixture
⇒0.42/2 × 100
⇒21%
Now suppose in 1.6g mixture,'x'g of Nacl,0.336g(21% of 1.6)NaHCO3 and rest Na2CO3 then
Wt of Na2CO3=1.6−0.336−x
⇒(1.264−x)g
Since both Na2CO3 and NaHCO3 react with HCl and therefore
Meq of Na2CO3+Meq of NaHCO3=Meq of HCl
x=0.151
Weight of NaCl=0.151g and % of NaCl=9.43%
Weight of NaHCO3=0.336g and % of NaHCO3=21.00%
Weight of Na2CO3=1.264−0.151
⇒1.113 and % of Na2CO3=69.57%