Both baking powder and baking soda are chemicals used to make cakes, muffins, or cookies, allowing the dough to rise and become lighter.

Sodium bicarbonate 
Is a chemical leaven. When in contact with some liquid acid (yogurt, lemon, vinegar, milk, etc.), it releases carbon dioxide, that makes the dough grow immediately.

Although it also releases an element with an unpleasant taste, that element will be neutralized by the acid that is also released. That is the reason to use it together with other acid elements (lemon, milk, cocoa).

Powdered yeast 
Is a chemical yeast composed of a mixture of sodium bicarbonate, an acidic element (as a rule, cream of tartar) and starch. The starch will absorb moisture from the air keeping the sodium bicarbonate and the acid elements separate and dry, preventing the sodium bicarbonate from reacting with the acid contained in the formula.

The reaction process of baking powder happens in two phases: sodium bicarbonate comes acts
around 60ยบ C, the remaining elements will take effect, making this process more time consuming.

The baking powder does not reach its potential until it comes in contact with the heat in the oven. Therefore, is extremely important to put the cake in the oven only when it is already at the desired temperature, and not to use hot ingredients when making the dough because it would make the yeast lose its effectiveness. Thus, yeast should always be the last ingredient to incorporate into the dough.

As a rule, we should use baking soda in cookies, cupcakes and muffins because we want a leaven that reacts in a short time. 
Baking powder is usually used to make cakes because the reaction time is longer and, given that the cake baking time is longer, this is the appropriate yeast.