Just half a cup maybe.
2 cups :)
The softest flour to use in baking should be semolina flour. When adding liquid to the flour, it is best to not overmix as the gluten doesn't form too much to make the result dense.
I don't know how much volume 4 oz. will be, but most recipes use the ratio of 1 teaspoon of baking powder to 1 cup of flour. Weigh the flour, measure it and find the amount of baking powder that way.
Most are made with yeast, so they don't contain any baking powder.
The amount of baking powder required depends entirely on what you intend to bake. Different types of cookies, muffins and other baked goods require different proportions of baking powder to flour.
I personally would never use baking soda or baking soda as a substitute for flour because they have different uses. Plus, that much baking soda or baking powder and no flour would leave a horrible taste in your mouth. Baking soda and baking powder are only used to make food rise while cooking and only a small amount of each is needed. While flour is more for adding density and flavour. If you're looking for a substitute for regular wheat flour, I would suggest oat flour, corn flour or soy flour.
2 grams
There is not a standard amount - it varies according to what you are cooking. If you wish to turn plain flour into self-raising, you need baking powder (which is a 1:3 ratio of bicarbonate of soda to cream of tartar). You need one teaspoon of baking powder to a cup of plain flour to create self-raising flour.
To make self rising flour .......1 cup flour add 1 teaspoon baking powder, 1/2 teaspoon salt and 1/4 teaspoon baking soda
For self rising flour 1 teaspoon.For biscuit mix 2 teaspoons.
The amount of flour used depends entirely on what you are baking. Refer to a dependable recipe. For example, if you are increasing fruit in a recipe from 2 cups to 4 cups, you are doubling the fruit, and all other ingredients, including flour, should be doubled as well.
Most recipes use 1 teaspoon of baking powder to 1 cup of flour.
Generally you use 1 to 2 teaspoons of baking powder to each cup of flour.