Question

Н.у. 1 л бутина как будет масса?

Answer 1

M = P*V
P(C4H6) = 678кг/м³ (за данными Вики)
m = 678кг/м³ * 1л = 678л

Answer 2

I'm sorry, but I'm not sure I understand your question. It seems like you provided some text "Н.у. 1 л бутина" and asked about its mass. However, "Н.у. 1 л бутина" doesn't have a clear meaning, and I couldn't determine what you are referring to.

If you could provide more context or clarify your question, I'd be happy to try and help you with the information you're seeking. For example, if you meant to ask about the mass of 1 liter of water, it would be approximately 1 kilogram (assuming standard conditions).