Monomer Units (1 Viewer)

[Eddy Q]

Ok, I got a question similar to this in an exam:

Draw the structural formula for a part of a polyethylene molecule showing three monomer units joined together.

Now I drew it like this(Sorry for shitty drawing, did it in paint haha):

My teacher said you had to draw like this(Again, sorry for shitty drawing):

Which one is correct? Or are they both correct?

 

[study-freak]

2nd one is correct because of the wording of the question
"Draw the structural formula for a part of a polyethylene molecule showing three monomer units joined together."

 

[Bored Of Fail 2]

fairly sure the second one is correct , remember when you polymerise ethene together the double bond opens,and thats where you get the two free electrons on the edges

 

[aimhigh10]

what about the brackets showing it is continuous though?

 

[ohexploitable]

for a part of a polyethylene molecule

In this case, your teacher is correct. However, if the question said, "draw the structural formula for a part of a polyethylene molecule showing [with] three monomer units joined together", then you would be correct.

 

[Eddy Q]

what about the brackets showing it is continuous though?

Draw the structural formula for a part of a polyethylene molecule showing three monomer units joined together.

No need for bracket since n=3

 

[study-freak]

what about the brackets showing it is continuous though?

i would put it, but i don't think it's really needed because we are only interested in a small part of the molecule
unlike (-monomer unit-)n structure

 

[aimhigh10]

Draw the structural formula for a part of a polyethylene molecule showing three monomer units joined together.

No need for bracket since n=3

i wonder how much more hsc stuff ive forgotten

 

[study-freak]

n=/=3. n>_3
but we are meant to show only 3 monomer units in our drawing

 

[Eddy Q]

In this case, your teacher is correct. However, if the question said, "draw the structural formula for a part of a polyethylene molecule showing [with] three monomer units joined together", then you would be correct.

Alright i found my exam and for thiss question i actually had to model(Since this exam was a practical exam):

Using the moly-mod kits provided construct the following compounds:

Ethen

The monomer for the polymer PVC and then 2 units of the polymer of PVC

Now the same scenario applies, I modelled the PVC like the 1st picture but the teacher said I had to model it like the 2nd.

 

[ohexploitable]

Your teacher is correct.

 

[study-freak]

Alright i found my exam and for thiss question i actually had to model(Since this exam was a practical exam):

Using the moly-mod kits provided construct the following compounds:

Ethen

The monomer for the polymer PVC and then 2 units of the polymer of PVC

Now the same scenario applies, I modelled the PVC like the 1st picture but the teacher said I had to model it like the 2nd.

The wording is not very precise but it said "polymer," which suggests long chain.
If there's only two monomer units in a molecule, they would have called it a dimer.

 

[Eddy Q]

Your teacher is correct.

Ok, thanks!

 

[OmmU]

The fact that it is an alkene would also tell you that those extra H atoms are not required. CnH2n. Therefore C6H12