Searching for the phrase "What chemical reaction happens when citric acid reacts with baking soda" in Google yields the following as the first hit.
The chemical reaction in this shows the following chemical equation which I have interpreted for you.
C6H8O7 (citric acid) + 3 NaHCO3 (baking soda) -> Na3C6H5O7 (salt) + 3 H2O (water) + 3 CO2 (gas bubbles))
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Now it's possible that the OP is asking what kind of a chemical reaction is the above? Exothermic or Endothermic?
Let's do a Google search with the phrase "Is citrc acid + baking sode an exothermic or an endothermic reactions?"
The first hit we get is:
https://saacs.chem.ufl.edu/wp-content/uploads/sites/51/2017/07/tempprobes.pdf?x48431
Which tells us that citric acid + baking soda is an endothermic reaction (the temperature falls with the reaction).
