The balance chemical equation for the conversion of sodium bicarbonate into carbonic acid is as follow,
NaHCO₃ + HCl → H₂CO₃ + NaCl
According to equation,
84 g (1 mole) NaHCO₃ produces = 62 g (1 mol) of H₂CO₃
So,
3.0 g of NaHCO₃ will produce = X g of H₂CO₃
Solving for X,
X = (3.0 g × 62 g) ÷ 84 g
X = 2.21 g of H₂CO₃
Hence, if the yield is ideal means, 100 % conversion takes place and all product is recovered then the amount of carbonic acid produced will be 2.21 g.