* Fizzing/Effervescence: The most obvious sign is the rapid release of gas bubbles. This indicates the formation of a new gas, carbon dioxide, as a product of the reaction.
* Dissolving: The tablet itself breaks down and disappears, indicating the formation of new chemical compounds.
* Temperature Change: The reaction may cause a slight temperature change, either a warming or cooling effect, depending on the specific reaction.
* Color Change: While Alka-Seltzer tablets are typically white, the solution may take on a slight yellow tint as the reaction progresses. This is due to the formation of new chemical compounds with different color properties.
What is happening?
Alka-Seltzer tablets contain sodium bicarbonate (baking soda) and citric acid. When they dissolve in water, these compounds react to produce carbon dioxide gas, sodium citrate, and water:
* NaHCO3 (sodium bicarbonate) + C6H8O7 (citric acid) → CO2 (carbon dioxide) + Na3C6H5O7 (sodium citrate) + H2O (water)
This reaction is exothermic, meaning it releases heat, explaining the potential temperature change you might observe.
