Hi! This is not a bug as much as a deliberate pedagogical choice. In our design discussions around instructional sequencing of the simulations, we talked about the tradeoffs of using high fidelity representations of the vinegar/baking soda reaction against a more developmentally conscious one.
When students arrive at this point in the curriculum, they will not covered any acid/base theory. Thus, they would not have access to any appropriate mental models to understand the dissociation of a weak acid that precedes the reaction of interest (that with bicarb).
This also complicates the calculation of enthalpy change in the reaction. We did not want students to have to consider the enthalpy change of the acid/base dissociation separate from the enthalpy change of the interaction with bicarb. Under the same simplifying assumptions, we also do not show the dissolving of sodium bicarb.
Postdoctoral Research Associate