A bridge must be made of metal or concrete or other materials that are strong enough to withstand the forces of the traffic passing over it. I doubt that the material could do that.
If the substance is a metal foam, it would make a rather hard cushion.
If the substance is too soft, it would make a cushion.
If the substance has the right combination of softness and elasticity so that it returns to its original shape when you get up, it might be a good material for a cushion.
Balanced equation: shown in photo
The formula is easy:
Gram formula mass
----------------------------
Emprical Formula
So if we plug in our own numbers,
114.0
--------
57.116
We get an answer of 1.99, which rounds to 2.
Then, we distribute based off of our empirical formula.
2(C4H9) becomes C8H18.
Our molecular formula is C8H18.
Hope I could help!