Пекарский порошок и разрыхлитель взаимозаменяемые добавки? или разные добавки к тесту?

Пе́карский порошо́к — искусственный разрыхлитель теста, применяемый при выпечке хлеба и приготовлении кондитерских изделий без дрожжей

Baking powder is a mixture of baking soda (sodium bicarbonate), an acid salt such as cream of tartar, and small amounts of starch, to simplify measuring and improve the stability of the mixture. It is used as a leavening agent in baking.

Carbon dioxide, the leavening gas produced by baking powder, originates from baking soda. Addition of an acidic compound promotes a rapid release of gas. The rate of gas release controls the size of the bubbles in the dough and influences the grain, volume, and texture of the baked product.

Some bakery products, such as pie crusts, are unleavened: they do not increase in volume while baking. Puff pastry doughs and cakes based on whipped eggs are leavened primarily by the expansion of water vapor and entrapped air during baking. Breads and sweet-dough pastries are usually yeast leavened. Most layer cakes, cupcakes, and many kinds of cookies are leavened by chemicals such as baking powder. Although yeast often produces a finer texture and flavor, baked goods made with baking powder are usually easier to prepare.

А разрыхлитель это непонятно что.

По сути, это одно и то же. То есть, пекарский порошок, это и есть разрыхлитель.

Надо посмотреть в википедии, но суть одна и та же.