Question

The atomic weights of C and H are 12 and 1, respectively. The chemical formula of polyethylene is (C2H4)n. The number average mean molecular weight of polyethylene with a degree of polymerization of 12,000 is:_____.

a. 120,000.
b. 336,000.
c. 280,000.
d. 296,000.

Answer 1

b. 336,000.

Step-by-step explanation:

Step 1: Calculate the molecular weight of the monomer

Polyethilene is a polymer with the formula (C₂H₄)ₙ, where C₂H₄ is the monomer and n is the number of monomers in the polymer. We can calculate the molecular weight of the monomer by addition of the weights of the atoms that form it.

MC₂H₄ = 2 × MC + 4 × MH

MC₂H₄ = 2 × 12 + 4 × 1 = 28

Step 2: Calculate the average molecular weight of polyethylene

The average degree of polymerization (DP) of polyethylene is 12,000. We can calculate the average molecular weight of polyethylene using the following expression.

DP = M(C₂H₄)ₙ/MC₂H₄

M(C₂H₄)ₙ = DP × MC₂H₄

M(C₂H₄)ₙ = 12,000 × 28 = 336,000