You can use any or all of these in cake baking. You cannot necessarily use them interchangeably and expect identical results.
It is quite usual to use both baking soda and baking powder in the same cake, especially if the recipe calls for an acid ingredient like fruit which will activate the baking soda, but in this case the volume of baking powder has usually been reduced. Baking powder mixes usually contain a small proportion of baking soda anyway.
Xanthan gum is most commonly used in making gluten-free products. Gluten is the protein found in flour. Heat, as in baking, toughens protein. Raising agents like baking soda and baking powder give off little bubbles of carbon dioxide during the baking process and these bubbles are held in place by the toughening gluten, rather like little balloons being blown up - this is what causes a cake to rise and hold its shape. Xanthan gum is used in a similar way to add thickness and volume to gluten-free products.
If you are wanting to add these raising agents to make a gluten-free product then read the label on the baking powder - it often contains gluten.
nope
The cake rises, causing it to be lighter and airier.
Most cake recipes call for baking powder. It will give more lift than soda.
Yes
No, there is no need to. The mix has baking powder already in it.
Self raising flour makes the cake rise, but if you don't have any you can use plain flour and baking powder which has the same effect. 225g plain flour and 4 teaspoons baking powder, will transform it into self raising flour.
Make one with each. The baking powder will perform better.
Yes, it's still effective. Refrigeration will not change the properties of baking soda.
It's not the milk alone that makes a cake rise. If the recipe includes milk it probably also contains either baking powder and/or baking soda. This combination of a base (Baking soda or Baking Powder) and an acid (milk) causes a slight chemical reaction which causes the cake to rise.
No. The two ingredients have entirely different functions. Baking powder contains an acid and baking soda, so that when the mixture is wetted the acid and soda react to form carbon dioxide bubbles which in turn causes the cake to rise. Xanthan gum, on the other hand, is a thickener, stabiliser or gelling agent which is stable at a wide range of temperatures, but is more viscous when cooler. If you used baking powder together with xanthan gum in the recipe, you could expect a very light and fluffy cake to come out of the oven, which would probably look more like a pancake if you chose to use neither.
Actually, both are activated by moisture( just a fun fact), but they are used under different conditions.Because baking powder contains baking soda. Also because baking soda does not contain the acidity to make a cake rise.
Baking soda is used in some cake recipes. Other recipes call for baking powder or simply beaten egg whites for leavening.