Question

Compute repeat unit molecular weights for the following: (a) poly(vinyl chloride), (b) poly(ethylene terephthalate), (c) polycarbonate, and (d) polydimethylsiloxane. please show equations used and calculations, thank you

Answer 1

(a) For poly(vinyl chloride), (-CH2-CH(Cl))n, each repeat unit consists of two carbons, three hydrogens, and one chlorine If AC, AH and ACl represent the atomic weights of carbon, hydrogen, and chlorine, respectively, then

m = 2(AC) + 3(AH) + (ACl)

= (2)(12.01 g/mol) + (3)(1.008 g/mol) + 35.45 g/mol = 62.49 g/mol

(b) For poly(ethylene terephthalate), (-CO-Ph-COO-CH2-CH2-O)n each repeat unit has ten carbons, eight hydrogens, and four oxygens. Thus,

m = 10(AC) + 8(AH) + 4(AO)

= (10)(12.01 g/mol) + (8)(1.008 g/mol) + (4)(16.00 g/mol) = 192.16 g/mol

(c) For polycarbonate, (-O-Ph-C(CH3)2-PhO-CO-)n each repeat unit has sixteen carbons, fourteen hydrogens, and three oxygens. Thus,

m = 16(AC) + 14(AH) + 3(AO)

= (16)(12.01 g/mol) + (14)(1.008 g/mol) + (3)(16.00 g/mol)

= 254.27 g/mol

(d) For polydimethylsiloxane, (-O-Si(CH3)2-)n each repeat unit has two carbons, six hydrogens, one silicon and one oxygen. Thus,

m = 2(AC) + 6(AH) + (ASi) + (AO)

= (2)(12.01 g/mol) + (6)(1.008 g/mol) + (28.09 g/mol) + (16.00 g/mol) = 74.16 g/mol