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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: tekki on November 22, 2020, 09:07:08 PM

Title: Question about calculating the molecular weight
Post by: tekki on November 22, 2020, 09:07:08 PM

Hi! Today I was doing my homework and I stuck on one exercise. I have to calculate the molecular weight of polypropylene, where n=320. Can someone help me and show me how can I calculate it? Here's the picture to this exercise.



I hope that someone can show me it! It'd mean the world to me!


EDIT: this is my attempt:

mC=12
mH=1
n=320

12*3+1*6=42u

42*320=13440

Answer: the molecular weight of polypropylene equals 13440

Title: Re: Question about calculating the molecular weight
Post by: Babcock_Hall on November 22, 2020, 09:26:01 PM

It is a Forum Rule (see red link above) that you must show your attempt at answering a problem before we can help you.

Title: Re: Question about calculating the molecular weight
Post by: tekki on November 22, 2020, 09:30:16 PM

oh, okay, so gimme a few second and I will post this here!

Title: Re: Question about calculating the molecular weight
Post by: tekki on November 22, 2020, 09:33:19 PM

Quote from: Babcock_Hall on November 22, 2020, 09:26:01 PM

It is a Forum Rule (see red link above) that you must show your attempt at answering a problem before we can help you.

I updated my post :)

Title: Re: Question about calculating the molecular weight
Post by: Borek on November 23, 2020, 03:34:46 AM

Very close, but technically incorrect.

What about the ends?

Title: Re: Question about calculating the molecular weight
Post by: tekki on November 23, 2020, 03:36:22 AM

Is it gon' be 13440u? Or you meant something else?

Title: Re: Question about calculating the molecular weight
Post by: Borek on November 23, 2020, 05:47:20 AM

Polymer chain doesn't start nor end with a sticking out unused bond.