The diene C4H6 is decomposed into elements at 70% which cause a volume increase of:
a) 140%
b) 150%
c) 170%
d) 240%

I think this is sort of a strange problem, What do you think is going on? What happens when butadiene is decomposed into it elements? What assumptions do you have to make in order to do the problem. Let us know your thoughts and we will help you with the more difficult aspects of the problem.

Honestly, I have no idea about the solution. I only know to write the formula, but it doesn't help very much since I don't know the elements that result and how to manage with volume increase. Please give some hints about these, I don't want to receive the solution and that's it, I just need to understand what should I do.

There are only two elements involved so that part should be easy (C4H6 --> 4C + 3H2) Which are gasses? What does "at 70%" mean? I guess it means that 70% of the starting material decomposes to the elements; You would have to assume that the other 30% does not react. You also must assume that the starting and final temperature and pressure are the same. Do you think these assumptions are true?
Now, remember that one mole of A and one mole of B will have the same volume in this problem. So all you have to do is count moles or liters. Remember too that if one mole of A turns into one mole of B there is 0% change of volume. Start with 100 L of butadiene and see what you get.

Ok. Thank you DrBob1!

What is the answer?