What should you use if a chocolate cake recipe calls for bouth baking soda and powder but only have powder?

Baking powder is a mixture of baking soda and an acid, such as cream of tartar. So, if you only have baking powder on hand, you can use it in place of baking soda by increasing the amount by three times for every teaspoon of baking soda.

So, if the recipe calls for 1 teaspoon of baking soda and 1 teaspoon of baking powder, you can use 2 teaspoons of baking powder instead.