Calculate the number of moles of NaHCO3 that reacted in each beaker. (The molar ratio between evolved CO2 and the bicarbonate, HCO3-, 1:1.)

For every mole of bicarbonate used, there is one mole of carbon dioxide evolved. In this case, let's say there are four moles of sodium bicarbonate used, there should be also four moles of carbon dioxide produced. This uses stoichiometry.