Question

The number average weight of a poly(styrene-butadiene) alternating copolymer is 1,350,000 gmol"!. Determine the average number of styrene and butadiene mer units per molecule.

Answer 1

8544

Step-by-step explanation:

Given:

An alternating copolymer,

thus, the number of both types of repeat units will be the same.

average weight of a poly(styrene-butadiene) = 1,350,000 g/mol

and,

there are 8 atomes of carbon and 8 atoms of hydrogen in the styrene repeat unit,

also, There are 4 atoms of carbon and six atoms of hydrogen in butadiene repeat units.

Therefore,

when the styrene-butadiene is combined the total number of carbon atoms in a molecule will be ( 8 + 4 ) i.e 12 atoms

and, the total number of Hydrogen atoms will be ( 8 + 6 ) i.e 14 atoms

Therefore, the total molecular weight will be

m = 12 × Molecular weight of the carbon + 14 × Molecular weight of the hydrogen

or

m = 12 × 12 g/mol + 14 × 1 g/mol

or

m = 158 g/mol

Now,

the average number of styrene and butadiene mer units per molecule will be

=
`\frac{\textup{1,350,000 g/mol}}{\textup{158 g/mol }}`

= 8544.30 ≈ 8544