Question

A 150 g sample of polyisoprene with a molecular weight of 1000 kg/mol is reacted with 0.75 g of sulfur to produce a rubber network. The product is a 70 cm long strip with a 0.93 g/cm3 density. If you suspend a 10 kg weight from one end of the strip, hung vertically, to what final length will the material stretch?

Note that the area to which the force is attached is not given but can be determined by (volume)/(length).

Answer 1

Moles of polyisoprene used = 150 g/10⁶ g.mol^-1 = 1.5*10^-8 mol

Moles of sulfur = 0.75 g/(32 g.mol^-1) = 0.0234375 mol

Volume of the sample = 10000 g/(0.93 g/cm³) = 10752.688 cm³

Now, the area of the strip = 10752.688 cm³/70 cm = 153.61 cm²

The final length should be greater than 70 cm.