What is the chemical composition of bread? molecular weight?

Bread is predominantly made up of carbohydrates, with protein, fiber, starch and fat to a lesser extent. There is no such thing as the "molecular weight of bread", because there isn't a "bread molecule". Bread is a mixture of molecules of different substances, i.e., carbohydrate molecules, protein molecules, etc.

Bread Chemical Formula

jstro is right. There's no such thing as bread molecule because bread is not a pure substance. It's a mixture. The chemical composition of bread depends on the ingredients used.