When an antacid tablet dissolves in water…?
Antacid are typically substances that when reacted with water, forms a base (pH > 7). In doing so, they typically would release a gas of some sort. That is why they sizzle when you put them in water. The lost of this gas makes the combined weight of the antacid and water go does down. (Note: not all antacids release gas when put in water) Reaction rate slows down because of 2 things. One, there is less of it to react with water. Two, the pH of the water slowly increases thereby slowing down the reaction. (Note: not all reaction rates decrease with time.
