Baking powder is a mixture of baking soda, starch and calcium acid phosphate. This mixture is used as leavening. Baking flour is ground wheat that covers all flours that are used in the baking process. It also includes cake flour, self0rising flour, and all-purpose flour. With different ingredients, the two serve entirely differently, and you cannot use them alternatively in any way. Baking mix has nothing to do with leavening as the baking powder is meant to.