Question

Group a used 5.00 moles of styrene and 0.0010 moles of benzoyl peroxide while group b used the same amount of benzoyl peroxide as group a but used only 1.50 moles styrene. What would the average molecular weight of each group's polymer sample be

Answer 1

Answer : Average molecular weight of group A = 104.0276 g

Average molecular weight of group B = 104.0920 g

Solution : Given, Moles of group A styrene = 5 moles

Moles of group A benzoyl peroxide = 0.0010 moles

Moles of group B styrene = 1.5 moles

Moles of group B benzoyl peroxide = 0.0010 moles

Molecular mass of styrene = 104 g/mole

Molecular mass of benzoyl peroxide = 242.23 g/mol

Formula used : Average molar mass = Total mass / Total moles

For group A,

Average molar mass of group A =
`\frac{\text{Total mass of group A}}{\text{Total moles of group A}}`

=
`(\left ( 5* 104 \right )+\left ( 0.0010* 242.23 \right ))/(5+0.0010)`

=
`(520+0.24223)/(5.0010)`

=
`(520.24223)/(5.0010)`

= 104.0276 g

Average molar mass of group A = 104.0276 g

For group B,

Average molar mass of group B =
`\frac{\text{Total mass of group B}}{\text{Total moles of group B}}`

=
`(\left ( 1.5* 104 \right )+\left ( 0.0010* 242.23 \right ))/(1.5+0.0010)`

=
`(156+0.24223)/(1.5010)`

=
`(156.24223)/(1.5010)`

= 104.0920 g

Average molar mass of group B = 104.0920 g