Question

the number-average molecular weight of a poly(acrylonitrile-butadiene) alternating copolymer is 1,000,000 g/mol; determine the average number of acrylonitrile and butadiene repeat units per molecule.

Answer 1

The average number of acrylonitrile and butadiene repeat units per molecule in an alternating copolymer with a number-average molecular weight of 1,000,000 g/mol is approximately 9331 of each, based on their individual molecular weights and the 1:1 alternating structure.

Step-by-step explanation:

To determine the average number of acrylonitrile and butadiene repeat units in an alternating copolymer with a number-average molecular weight of 1,000,000 g/mol, we first need the molecular weights of the acrylonitrile and butadiene monomers.

Acrylonitrile (C3H3N) has a molecular weight of approximately 53.06 g/mol, and butadiene (C4H6) has a molecular weight of approximately 54.09 g/mol. Since it's an alternating copolymer, we know there will be one acrylonitrile unit for every butadiene unit.

The combined weight of one acrylonitrile unit and one butadiene unit is 53.06 g/mol + 54.09 g/mol = 107.15 g/mol. Therefore, the total number of repeat units in the polymer molecule will be 1,000,000 g/mol divided by 107.15 g/mol/monomer pair, which equals approximately 9331 monomer pairs or 9331 acrylonitrile and 9331 butadiene units.

Answer 2

To determine the average number of acrylonitrile and butadiene repeat units per molecule in the poly(acrylonitrile-butadiene) alternating copolymer, we can use the number-average molecular weight and the monomer composition of the copolymer. Assuming a certain weight percentage for each monomer, we can calculate the average number of repeat units per molecule using the molecular weights of the monomers.

Step-by-step explanation:

To determine the average number of acrylonitrile and butadiene repeat units per molecule, we need to know the monomer composition of the poly(acrylonitrile-butadiene) alternating copolymer. From the name, we can tell that the copolymer consists of repeating units of both acrylonitrile and butadiene.

The number-average molecular weight of the copolymer is given as 1,000,000 g/mol. This means that on average, each molecule of the copolymer weighs 1,000,000 g/mol.

To calculate the average number of repeating units of each monomer per molecule, we need to determine the composition of the copolymer by weight. Let's assume that the copolymer is 80% acrylonitrile and 20% butadiene by weight. This means that 80% of the total weight of the copolymer is due to acrylonitrile and 20% is due to butadiene.

Now we can calculate the average number of acrylonitrile repeat units per molecule:

(0.8 ×1,000,000 g/mol) / (MW of acrylonitrile) = number of acrylonitrile repeat units per molecule

Similarly, we can calculate the average number of butadiene repeat units per molecule:

(0.2 × 1,000,000 g/mol) / (MW of butadiene) = number of butadiene repeat units per molecule

By substituting the respective molecular weights of acrylonitrile and butadiene into the equations, we can find the average number of repeat units of each monomer per molecule.