baking soda or sodium bicarb is what is known as an amphoteric substance that can buffer both acid and alkali so is used in antacid preperations. Alka selzer the antacid preparation is sodium bicarb aka baking soda
No - although I have seen some research on windsucking/cribbing being related to excess acidity in the stomach so horses are being fed similar substances to seek to reduce acidity to see if it helps prevent the vice. Some New Zealanders seem to have started it by feeding Tums etc. Others responded by pointing to the old practice of feeding baking soda for same reason.