Can you use the baking soda have in my fridge to bake cookies?

Baking soda that has been exposed to humidity can lose its leavening power making it not as effective. For this reason, you should either purchase a fresh box of baking soda or conduct a test to make sure its still good before adding it to a recipe. To test your baking soda's validity, mix a tsp baking soda to 1 tablespoon of white vinegar. If it vigorously bubbles, its ready to use.