A guided-inquiry lab, suitable for first-year general chemistry or high school advanced placement chemistry, is presented that uses only inexpensive, store-bought materials. The reaction of sodium bicarbonate (baking soda) with aqueous acetic acid (vinegar), under the constraint of the challenge to completely fill a sealable plastic bag with the gaseous carbon dioxide product, is presented to students of chemistry. Students must marshal their knowledge of non-STP gas stoichiometry, including the often misunderstood concept of limiting and excess reagents, to successfully complete the task. This contribution is part of a special issue on teaching introductory chemistry in the context of the advanced placement (AP) chemistry course redesign.