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.
This depends a lot on what the powder is - since grams is a measure of weight and teaspoons is a measure of volume, there is not a standard conversion (it varies a lot depending on what substance your are measuring). However, a teaspoon of a ground up spice or baking powder will usually weigh around 4-5 grams (approximately).
There are 0 calories in Baking Powder...;)
1 Pounds = 453.59237 Grams, so you would need to measure 113.4 teaspoons of your ingredient to get a pound. Don't lose count!
About 5 grams
20 Grams.
2 grams
Yes, salt generally weighs more than both sugar and baking soda because salt is denser. A teaspoon of salt will weigh more than a teaspoon of sugar or baking soda.
100,000,000,000,000 pounds
About 3.25g, given a 5mL teaspoon and a creatin density of 1.3.
This question makes no sense. Teaspoons are a measure of volume and grams are a measure of weight. Apples and Oranges. A teaspoon of sugar will not weigh the same as a teaspoon of water.
ANSWER You need to know the density of foodstuff. For example 1 US teaspoon of milk = 4.9 g 1 US teaspoon of milk powder = 2.4 g 1 US teaspoon of salt = 6.2 g and so on.