When 8.4g of NaHCO3 is added to a solution of CH3COOH weighing 20g. It is observed that 4.4 g of CO2 is released into atmosphere and a residue is left behind. Calculate the mass of the residue by applying law of conservation of mass?

The mass of the residue, or sodium acetate solution, should be ##"24.0 g"## of sodium acetate solution.

In this reaction, sodium bicarbonate reacts with acetic acid to produce sodium acetate, carbon dioxide, and water. The carbon dioxide bubbles out of solution, leaving behind a sodium acetate solution.

##"NaHCO"_3 + "CH"_3"COOH"####rarr####"CH"_3"COONa + CO"_2 + "H"_2"O"##

According to the law of conservation of mass, the total mass of the reactants equals the total mass of the products. The reactants are 8.4 g sodium bicarbonate and 20 g acetic acid solution. The total mass of the reactants is:

##"8.4 g NaHCO"_3 + "20 g CH"_3"COOH"## = ##"28.4 g total mass of reactants"##

The total mass of the products must equal the mass of the reactants. If we subtract the mass of carbon dioxide from the total mass of the reactants, we can determine the mass of the residue, which is basically a sodium acetate solution.

##"28.4 g total mass of reactants - 4.4g CO"_2"## = ##"24.0 g of residue" ("sodium acetate solution")##