is baking soda and baking powder the same thing? im making lemon tarts

Baking soda requires an acidic ingredient (buttermilk, lemon) to help create the desired rising effect. Baking powder already has acid in its makeup and can be activated by adding a liquid (milk ,water)

You can get away with using powder instead of soda. However you will need to add an acid (cream of tartar as an example) to have baking soda work like powder

Not the same at all, both are for levening but if you substitute baking powder for soda, you add more and omit any salt the recipe calls for.

No, they are not the same. What does your recipe call for?