Discover what happens when baking soda is added to mustard?
1.) Pour some mustard into the clear cup. The amount is not crucial.
2.) Add 1 teaspoon of baking soda to the cup and stir briefly.
3.) Stop stirring and observe
The mustard will rise in a dramatic fashion due to the presence of vinegar in mustard. The reaction between the vinegar and baking soda will produce carbon dioxide gas, which causes the mustard to rise.
The reaction will continue until all of the vinegar is used up. In this case, the baking soda will be in excess. Since the vinegar is used up, it is the limiting reactant.