Compute the repeat unit molecular weight of polystyrene. (b) Compute the number-average molecular weight for a polystyrene for which the degree of polymerization is 23000.

Answer :

(a) The repeat unit is, styrene

(b) The number-average molecular weight is, 2392000 g/mol

Explanation :

First we have to calculate the repeat unit molecular weight of polystyrene.

As, the repeat unit is, styrene having chemical formula

Molecular weight of repeat unit = 8 × C + 8 × H

Molecular weight of repeat unit = 8 × 12 g/mol + 8 × 1 g/mol

Molecular weight of repeat unit = 104 g/mol

Now we have to calculate the number-average molecular weight.

Number-average molecular weight = Average repeat molecular weight × Degree of polymerization

Number-average molecular weight = (104 g/mol) × (23000)

Number-average molecular weight = 2392000 g/mol

Thus, the number-average molecular weight is, 2392000 g/mol

1. 1 mole of anything contains 6.022x10^23 pieces  

d  

2. a  

3. c, number  

5. 1.24x10^24atoms / 6.022x10^23atoms/mole = 2moles h2 atoms  

6. fe2br3 mass = 2moles x mass fe + 3 moles x mass br  

molar mass = grams / number of moles = g/mole  

to find moles = g / molar mass  

to find mass = g = molar mass / moles