The correct answer is option 1. Butane and 2-butene have the same total number of carbon atoms. They both have four carbon atoms. They differ in there structure since the latter has double bonds on it. As a result of the different structure, they also have different properties.
I think you just do 11.29 multiplied by 186 since to find density you divide mass by volume. So 186 divided by x is 11.29. So in conclusion the volume would be 2,099.94mL
