Help with chemistry lab?

Okay so I'm doing a lab that is a simulation of an airbag using HCl and NaHCO3(Baking soda). So I poured a pipet full of hydrochloric acid onto (3.0,3.5, and 4.0) grams of baking soda in a closed bag, and watched it inflate. Which one is supposed to be the most plump without overinflating? What is the limiting reactant in the equation? What is the theoretical yield, and the percent yield? I suck at chemistry so you guys gotta save me on this one.