Chemistry: does baking soda deteriorate?

Self-tutoring about household chemistry: the tutor looks into the idea that baking soda can lose its effectiveness while just sitting on the shelf.

Nowadays, one hears surprising claims quite often, so might be atuned to the “disbelief” setting. When I heard about baking soda “going bad” on the shelf, I put it in the “doubtful” column, then continued with my day. Yet, I kept hearing it. Realizing that, if such were possible, it would make a good post, I decided to look into it.

I realized I’ve even written a related post back on December 11, 2021. However, that post focuses on a situation where baking soda is heated in water on the stove – quite a different scenario from it decomposing in the box on the shelf.

While it seems hard to imagine baking soda going bad in a harmful way, the sources I’ve read suggest that baking soda might lose its leavening ability, sitting on the shelf, especially once opened. Even that seems unlikely to me, but a decomposition is theoretically possible: the sodium bicarbonate can break down into sodium carbonate plus water plus carbon dioxide:

2NaHCO₃ → Na₂CO₃ + CO₂ + H₂O

Over the past ten years I’ve done a lot of baking. Sometimes I’ve used fresh baking soda, sometimes old. Yet, I can’t recall baking soda letting me down; I’d use two-year-old baking soda from the shelf with confidence.

A caveat might be that if someone lived in a warm place, like South Carolina, the environmental heat there might be enough to cause sufficient decomposition of baking soda for one to notice a decline in its performance – possibly.

Source:

chem.libretexts.org

marthastewart.com