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Can someone explain why the answer is c. Shouldnt the h2o be cancelled out in the middle? Where did the oxygen cone from?
To be completely honest, whilst I can't really answer your question directly, I can answer the question by elimination. I think that's the best way to deal with this question anyway.
Firstly, by looking to the Polymer, we know that one monomer should be 5 carbon lengths long, and one should be 4 carbon lengths long. This immediately rules out A or D, leaving us with B or C.
Now, let's get of an OH from one monomer, and a H from another monomer. We know that a H2O is condensed out of the monomers somewhere, so this is a fair thing to do. According to B, this would result in one of two things: either BOTH monomers still have an OH group, or one doesn't an an OH group, and one has two. Looking to the Polymer, we can't see a single OH in sight. As such, B doesn't make any sense; we should see some left over.
Well damn. Actually, C has two OH in each monomer. Maybe that means two Water molecules are eliminated? I'm stumped, sorry I'm not great at visualising Chemistry stuff like this. Maybe someone can come help us out?