Question: how much baking powder for 1/2 teaspoon baking soda?
Answer: Yes, as long as there is enough of an acidic ingredient to make a reaction (for 1/2 teaspoon baking soda, you need 1 cup of buttermilk or yogurt or 1 teaspoon lemon juice or vinegar). And remember that baking soda has 4 times the power of baking powder, so 1/4 teaspoon soda is equivalent to 1 teaspoon of baking powder.