I've just downloaded a recipe to make some banana oat muffins and it's from an American website and says to use 2 tsp baking powder and 1 tsp baking soda. I thought they were the same thing Are they not?
You can use baking soda on its own if your mixture is quite acidic -- so if your mixture contains a fair bit of (for example) yogurt, chocolate, buttermilk or honey you often won't need baking powder and can just use baking soda. But (unless you're making things up from scratch) that will be stated in the recipe.
It's banana oat muffins. The recipe asks for all purpose flour bt maybe that's an American thing. I have baking powder but no baking soda although I do have bicarbonate of soda so will I use that instead f the baking soda?