To find out whether your baking soda has gone bad, you will need some acid, such as vinegar. Baking soda reacts with the acidic ingredients in your recipes to produce carbon dioxide gas. Those bubbles of gas are what act to make the dough rise.
Toss a spoonful of baking soda into a bowl.
Add a splash of vinegar or lemon juice.
If the mixture fizzes heavily, the baking soda is still good.
If you don't get much of a fizz, your baking soda has gone bad.
Use the rest of the box for cleaning, and buy another box for your baking.