(a) `NaHCO_(3)+CH_(3)COOHrarr CH_(3)COONa+H_(2)O+CO_(2)`
Initial mass `= 4.2+10 = 14.2`
Final mass `= 12+2.2= 14.2`
Thus, during the course of reaction law of conservation of mass is obeyed.
(b) `NaHCO_(3)+CH_(3)COOHrarrCH_(3)COONa+H_(2)O+CO_(2)`
Initial mass `= 6.3+15= 21.3`
Final mass `= 18.0+` mass of `CO_(2)`
According to law of conservation of mass:
`21.3 = 18.0+` mass of `CO_(2)`
`:.` Mass of `CO_(2)= 3.3 g`