Question

Consider the vulcanization of 20 kg of polybutadiene with 4.8 kg of sulfur. What fraction of the possible crosslink sites is bonded to sulfur crosslinks, assuming that, on average, 4.5 sulfur atoms participate in each crosslink?

A) 0.3
B) 0.6
C) 0.9
D) 1.2

Answer 1

To determine the fraction of crosslink sites bonded with sulfur, calculate the moles of sulfur used, and then determine the number of crosslinks. This is compared to the total number of potential crosslink sites in the polybutadiene.

Step-by-step explanation:

The question asks us to calculate the fraction of the possible crosslink sites in polybutadiene that are bonded to sulfur crosslinks during vulcanization. First, we determine the moles of sulfur used by dividing the mass of sulfur reacted, 4.8 kg (4800 g), by its molar mass (32.07 g/mol). Then we calculate the number of crosslinks by dividing the moles of sulfur by the average number of sulfur atoms per crosslink. This number should then be divided by the total possible number of crosslink sites, which is given by the moles of polybutadiene multiplied by the number of possible crosslink sites per mole (which is not provided in the question and should be known from the chemical structure of polybutadiene or additional stoichiometric information).