Since baking soda and citric acid in water make a good fizzy reaction, I thought it would be interesting to make tablets of each, to add to water.
I recently figured out how to make baking soda tablets, and was able to use the same method to make citric acid tablets. The tablets contain citric acid and gelatine powder in equal quantities, with a few drops of food colouring.
The reaction when added to water seemed slower than just the ingredients alone, probably because of the gelatine.
Here is the reaction formula:
3NaHCO3 + C6H8O7 → 3Na+ + C6H5O73- + 3H2O + 3CO2
The gas is the CO2.
After about 1/4 of an hour the mixture looked like this: